DESCRIPTION

Title of Invention

A METHOD USED FOR A MOBILE COMMUNICATIONS SYSTEM, A USER EQUIPMENT USED IN A MOBILE COMMUNICATIONS SYSTEM AND A SIMULATOR USED FOR A MOBILE COMMUNICATIONS SYSTEM

Technical Field

[0001]

The present invention relates to a method used for a mobile communications system, a user equipment used in a mobile communications system and a simulator used for a mobile communications system.

Background Art

[0002]

In traditional mobile communication links, antennas at access nodes (e.g. at a base station (BS)) are located at a relatively high elevation (i.e. relatively high above the ground), and antennas of user equipments (UEs) or mobile terminals (MTs) are located at a relatively low elevation (i.e. close to the ground). Note: the terms user equipment (UE) and mobile terminal (MT), and plural versions of said terms, are used interchangeably herein. The low antennas at the UE, and also objects surrounding or around the UE in the environment, can often cause signals transmitted from the BS to the UE to be scattered in the local vicinity of the UE. This creates a local scattering environment around the UE and causes small-scale variations in the signal transmitted between the BS and the UE. Since an access node such as a BS will generally be located on higher elevated ground (generally higher than surrounding objects), it may see a scatterer distribution in a limited angular region, far away from the BS. This type of scattering environment that exists between the BS and the UE is well modelled by the so called 'single-ring' scattering concept, which considers a ring of local scatterers around the UE while the BS sees a scatterer distribution in a limited angular region.

[0003]

On the other hand, when both ends of the wireless communication link (i.e. the transmitter-end and the receiver-end) are located at a low elevation (e.g. close to the ground), both ends may be surrounded by objects creating local scattering at both ends. Therefore, the 'single-ring' scattering model may no longer be appropriate to describe this type of environment. A concept of 'double-ring' scattering has been developed to model the environment where both ends of the wireless communication link are surrounded by local scatterers. See Byers, G.J., Takawira, F., "Spatially Temporally Correlated MIMO Channels: Modeling and Capacity

Analysis", IEEE transactions on vehicular technology, vol. 53, No. 3, May 2004, and Patel, C.S., Stuber, G.L., Pratt, T.G., "Simulation of Rayleigh-Faded Mobile-to-Mobile Communication Channels", IEEE transactions on communications, vol. 53, No. 11, Nov 2005.

[0004]

Fig. 1 illustrates a double-ring scattering model (100) for a single-input-single-output (SISO) system in which both the transmitter and the receiver are moving. The model (100) in Fig. 1 includes a transmitter (101.a), which may be the transmitter of a UE. The transmitter (101.a) is moving at a velocity \ _Tx in the direction θ _Τ ^ν _χ with respect to the transmitter's array broadside. There is also a receiver (lOl.b), which may be the receiver of another UE. The receiver (101. b) is moving at a velocity v _& in the direction with respect to the receiver's array broadside. Two rings of scatterers, namely a Tx-scattering-ring (102. a) and a Rx- scattering-ring (102.b) are located around the transmitter (101. a) and the receiver (101. b) respectively. A ray travels from the transmitter (101. a) to the I ^th transmit scatterer TS _t (104) located in the Tx-scattering-ring (102. a) via the I ^th path (103) and then continues to the m' ^h receive scatterer RS _m (106) located in the Rx-scattering-ring (102.b) and further continues to the receiver (lOl.b) via the m' ^h path (105). The wave travelling from the I ^th transmit scatterer TS _/ (104) to the m ^,h receive scatterer RS _m may be further scattered by remote scatterers, however, the pathloss may limit the contribution from the remote scatterers. The angle of departure (AoD) of the ray from the transmitter (101. a) to the l' ^h scatterer TS _f (104) is denoted by θ _{Ι ΑοΌ} , and the angle of arrival (AoA) of the ray scattered from the m' ^h scatterer

RS _m (106) and reaching the receiver (lOl.b) is denoted by 9 _{m AoA} . The channel coefficient (channel gain) for this model is given by:

Kt) =

Equation 1

Where:

• / refers to the paths (103) travelling from the transmitter (101. a) to the L scatterers (104) located within the Tx-scatterer-ring (102.a),

• m refers to the paths (105) travelling from the M scatterers (106) in the Rx-scatterer-ring (102.b) to the receiver (lOl.b),

• k is the wave number and has value of k =— ,

λ

• exp[/£ cos(0, _AoD - θ^ _χ )ί] accounts for the phase shift due to mobility of the

transmitter ( 101. a),

· exp[j ^' & || cos(6 _{m AoA} - θ^)ί accounts for the phase shift due to mobility of the receiver (lOl .b),

• exp[ ^ _m ] accounts for the joint phase shift of the scatterers at transmitter TS, and at receiver RS _m ,

• exp[j<p, _m ] accounts for the phase shift due to path length from Tx (transmitter)-to- TS, (transmitter scatterer)-to- RS _m (Receiver scatterer)-to-Rx(Receiver), and

• P is the total power of the path (including scatterer gains).

[0005]

And, in Fig.1, d[ ^s is distance from the transmitter (101. a) to the I ^th scatterer TS, (104), d _lm is distance from the I ^th scatterer TS, (104) to the m' ^h receive scatterer RS _m (106), and d is distance from the m' ^h receive scatterer RS _m (106) to the receiver (101. b).

[0006]

The model (100) in Fig. 1 considers only local scattering and assumes an infinite number of scatterers around the transmitter (101. a) and around the receiver (lOl.b). In addition, the mobile environment is assumed to be quasi-stationary for short period of times.

[0007]

Fig. 2 shows a model (200), which is an extension of the above SISO model (100). The model (200) is for a multiple-input-multiple-output (MIMO) system with two transmit antennas and two receive antennas (i.e. where the transmitting UE has two transmit antennas and the receiving UE has two receiving antennas). The transmitter (201.a) is moving at a velocity v _Tx in the direction θ _Ύ ^ν _χ with respect to the transmitter's array broadside. The receiver

(201.b) is moving at a velocity in the direction with respect to the receiver's array broadside. The I ^th path (203) means path from the transmitter (201. a) to the /" ^* transmit scatterer TS, (204), and the m' ^h path (207) means path from the m' ^h scatterer RS _m (206) to the receiver (201.b). The angle of departure (AoD) of the ray from the transmitter (201.a) to the l' ^h scatterer TS, (204) is denoted by θ, _Αοϋ , and the angle of arrival (AoA) of the ray scattered from the m' ^h scatterer RS _m (206) and reaching the receiver (201.b) is denoted by

9 _{m AoA} . The spacing between the two transmit antennas is δ _τ (205. a) and the spacing between the two receive antennas is S _R (205.b). For the purposes of the model (200) in Fig. 2 it is assumed that the rays travelling from different antenna elements (Tl or T2) to a particular Tx scatterer (204) in the Tx-scatterer-ring (202.a) have approximately the same angle of departure (AoD), and the rays arriving at different antenna elements (Rl and R2) from an Rx scatter (206) in the Rx-scatterer-ring (202. b) have approximately the same angle of arrival (AoA). Thus, the narrowband flat fading channel gain of the path between a transmit antenna element 5 (e.g. Tl or T2) and a receive antenna element u (e.g. Rl or R2) can be written as:

p L M

h _{u s} {t) = ∑ exp[/(* II y _Tx || cos(0 _UoO - 0 _T ^v _x )t ₊ k || ν _Λ || cos^ - 0^ +0, ^ )]

Equation 2

[0008]

Here, is the phase shift due to path length from T _s -to- TS, -to- RS _m -to- R _u . For example,

expL ¹ ;! ] = expL/W + d, _m + d£ )] e p[ ¾ ] = expL/tt(½ sin(0, _AoD ) + d* + d, _m + d + S _R sin(0 _{m AoA} ))]

Equation 3

Where

· d f is distance from the Tl to the l' ^h scatterer TS, (204),

• d _im is distance from the scatterer TS, (204) to the m' ^h receive scatterer RS _m (206), and

• d i is distance from the m' ^h receive scatterer RS _m (206) to the Rl .

[0009]

Therefore, the channel gain between transmit antenna element s and receive antenna element u can be re-written as - )t +0 _{l m} )) x

Equation 4 Where

• δ _γ represents the spacing between transmitter antenna element s and the reference

transmitter antenna element (say antenna 1 or Tl), and

• δ represents the spacing between receiver antenna element u and the reference receiver antenna element (say antenna 1 or Rl).

Citation List

Non Patent Literature

[0010]

NPL 1: G.J., Takawira, F., "Spatially Temporally Correlated MIMO Channels: Modeling and Capacity Analysis", IEEE transactions on vehicular technology, vol. 53, No. 3, May 2004.

NPL 2:Patel, C.S., Stuber, G.L., Pratt, T.G., "Simulation of Rayleigh-Faded

Mobile-to-Mobile Communication Channels", IEEE transactions on communications, vol. 53, No. 11, Nov 2005.

Summary of Invention

Technical Problem

[0011]

The related models discussed above are for narrow band systems with an infinite number of scatterers. Such models may not be suitable for wideband systems such as 3 GPP LTE/LTE-A systems. This may be due, for instance, to the multipath fading environment. Thus, there may be a need for a new reference channel model for wideband systems such as 3 GPP LTE/LTE-A systems in which both the transmitter and the receiver have antennas at relatively low elevations and where both are moving, such as in device-to-device (D2D) commumcation.

[0012]

As the name suggests, device-to-device (D2D) commumcation systems (or D2D communication) refers to the scenario where one Mobile Terminal (MT) directly communicates with another MT creating a local communication environment. This scenario generally involves low elevated antennas (i.e. antennas relatively close to the ground) at both the transmitter(s) of one MT and the receiver(s) of the other MT. It will also generally be the case that the transmitter(s) will be moving, as will the receiver(s). According to 3 GPP, D2D communication may operate in wideband systems such as LTE/LTE-A. Therefore, multipath fading is a likely fading scenario that may appear in the D2D communication environment. For a proper study and evaluation of technologies proposed for D2D communication, especially D2D communication within 3 GPP LTE/LTE-A wideband systems, there would appear to be a need for a channel model that is simple but sufficiently appropriate for the purpose of generating accurate channel coefficients, for example, for use in evaluating technologies intended for D2D communication in wideband multipath fading environments by simulation.

[0013]

It is to be clearly understood that mere reference herein to previous or existing apparatus, products, systems, models, methods, practices, principles, publications or other information, or to any associated problems or issues, does not constitute an acknowledgement or admission that any of those things individually or in any combination formed part of the common general knowledge of those skilled in the field, or that they are admissible prior art.

Solution to Problem

[0014]

In a first form, the present invention relates broadly to a method used for a mobile communications system, the method including:

th P

obtaining a channel gain according to values for power of an ⁿ path " , a direction of Tx motion ^Tx , a spacing between antenna elements at a transmitter and a reference

fi ^s θ ^ν

transmitter antenna τ ₅ a direction of Rx motion ^¾ , and a spacing between antenna elements at a receiver and a reference receiver antenna R .

[0015]

The channel gain may be expressed as ,

P. M exp[/(* II _a II cos(6^ _oD - e _x )t + * II ν _Λ II cos(0„ _{m A} - θ^ί +0 _nJ ] x

=1 m=l expLW sin(0„ _UoD ) + S _R ^U sm(0 _{n m AoA} ))]xexp[j<p _{nJ m} ] where L is a number of scatterers per Tx-cluster,

M is a number of scatterers per Rx-cluster, is a velocity of the transmitter, is a velocity of the receiver,

Θ I'h

,ι,ΑοΌ j _{s m} angle ₀ f departure (AoD) of a ray from a transmitter to '

th

Tx-scatterer ' located in an ⁿ Tx-cluster, θ RS n,m,AoA i _{s m} angle of arrival (AoA) of a ray from ^m Rx-scatterer ^m th

located in an ⁿ Rx-cluster to a receiver,

t is time,

@n,i,m j _{s a} p _{nase s} h f¾ due to ^ Tx-scatterer located in the ⁿ ' ^h Tx-cluster and ^m ' ^h Rx-scatterer ^ ^m located in the ⁿ ' ^h Rx-cluster,

Ψη,ι,π, i _{s a} ph _a s _e shift due to a path length from Tx-to- ' -to- ^m -to-Rx, and

* is a wave number and has a value of ^λ , ^ being a wavelength.

[0016]

The channel gain may be expressed as where ^L is a number of scatterers per Tx-cluster,

M is a number of scatterers per Rx-cluster,

v ₇ ^tx is a velocity of the transmitter, r** is a velocity of the receiver,

Θ D) of a ray f t*rom a transmitter to ' 1 ^th n .AoD i _s angle of departure (Ao

'T'c th

Tx-scatterer ' located in an ⁿ Tx-cluster,

Θ R

n,m,AoA ig ^ angle of arrival (AoA) of a ray from ^m Rx-scatterer located in an ⁿ ' Rx-cluster to a receiver,

t is time,

^ _n ,i,m i _{s a} phase shift due to ^ Tx-scatterer ^ located in the «'* Tx-cluster and ^m ' ^h Rx-scatterer ^ ^m located in the Rx-cluster,

Ψη,ι,η, i _{s a} phase shift due to a path length from Tx-to- ' -to- ^m -to-Rx, k is a wave number and has a value of λ ^ λ being a wavelength,

G (Θ )

\ η,ι,Αοϋ I i _{s a} transmitter antenna gain of each array element, G (Θ ^

Rx K n,m,A A ) j _{g a receiver} antenna gain of each array element, and is a shadow fading factor for ⁿ path.

[0017]

The channel gain may be expressed as

where ^ is a number of scatterers per Tx-cluster,

M is a number of scatterers per Rx-cluster, v ^¾ is a velocity of the transmitter, V ^rx is a velocity of the receiver,

&r,,i,AoD i _{s 0} f departure (AoD) of a ray from a transmitter to

ye th

Tx-scatterer ' located in an ⁿ Tx-cluster,

Θ 'h scatterer /?<? n,m,AoA j _g ^ gngig ₀ f arrival (AoA) of a ray from ^m Rx- ^m th

located in an " Rx-cluster to a receiver,

t is time,

&n,i,m j _{s a} ph _{ase s} hif¾ due to ^ Tx-scatterer located in the ⁿ ' ^h

th ? th

Tx-cluster and ^m Rx-scatterer ^m located in the ⁿ Rx-cluster, ψ ^η, ι ^,πι a phase shift due to a path length from Tx-to- ' -to- ^m -to-Rx, k is a wave number and has a value of λ ^ λ being a wavelength, θ _{η ί} is a phase shift due to Tx-scatterer located in the ⁿ ' ^h

Tx-cluster,

0 _{n m} is a phase shift due to ^m ' ^h Rx-scatterer ^ ^m located in the

Rx-cluster,

φ„,ι =kd _nj , d^i being a distance between a transmitter and ¹ Tx-scatterer Γ ^5/ located in the »* Tx-cluster, dn m being a distance between a receiver and ^m Rx-scatterer located in the ⁿ Rx-cluster, and

d"

is a phase shift due to distance between the ⁿ -th Tx-cluster and the " -th Rx-cluster.

[0018]

The channel gain may be expressed as

p ( L

- _r ,✓ I∑ ^εχ Ρ[- ( || ^ν 7> 1 cos(i? _ , ^ - ¾ )t + kS _T ' sin(0„ , yloD X

∑expL/(*||v _ft ll cosC^^ - <¾,)* + kS sin^^) + <D where ^L is a number of scatterers per Tx-cluster,

M is a number of scatterers per Rx-cluster,

k is a wave number, v ^?i is a velocity of the transmitter, v ^¾ is a velocity of the receiver,

&nj,AoD i _s ^ angle ₀ f departure (AoD) of a ray from a transmitter to ^

fc th

Tx-scatterer ' located in an ⁿ Tx-cluster,

θ

n,m,AoA j _s ^ angle of arrival (Ao A) of a ray from an ^m Rx-scatterer /?v ^m th

located in an ⁿ Rx-cluster to a receiver,

t is time, k is a wave number and has a value of λ ^ λ _De i _n g a wavelength,

^*".' and ^"' ^m are single valuables that represent θ _η ,ι + ψη,ι and 6 _n ,m + q)n,m + respectively, and are assumed to be uniformly distributed over \ ^~π ^ , φ _η ,\ -kd , being a distance between a transmitter and ^ Tx-scatterer

' located in the ⁿ Tx-cluster,

th

being a distance between a receiver and ^m Rx-scatterer (A

™ located in the " Rx-cluster, and

d"

is a phase shift due to distance between the ⁿ -th Tx-cluster and the ⁿ -th

Rx-cluster. [0019]

The method used for a mobile communications system may further comprise: generating AoD ^ ^» - ^AoD of the transmit cluster and AoA ^ ^» · ^ΑοΛ from the receive cluster independently from distributions ^ ^c ^ and ^ ^c ^ , respectively; generating ¹ AoD offsets ( ^ ^!>AoD ^ ^" ' ^ ) of the Tx cluster and ^M AoA

Δ m = 1,.., M _th

offsets ( ^{m >A0A} ) of the ⁿ Rx cluster independently from distribution of scatterers within a cluster ^ ^s ^ ^s ^ ;

a a

obtaining ^L AoDs ( ⁿ - ^oD ) and M AoAs ( ⁿ >™- ^o ) using

enJ,AoD = ^θ η,ΑοΟ ^{+ Δ} /, οΰ ∞d θη,π>,ΛοΛ = ^θ η,ΑοΑ + m,AoA \ ³¹¹⁽¹

generating phase changes Φ„ = Ι,.,.,Ζ and 0„ _m , m = 1,..., independently from a uniform distribution over [-π, π) .

[0020]

θ θ

AoD ^η · ^Α °°, AoA ^η · ^ΑοΑ , the ^L AoD offsets, the ^M AoA offsets, and the phase changes may be generated using random values.

[0021]

The method used for a mobile communications system may further comprise: assuming symmetric distributions for AoD and AoA such that Pc ) ^~ Pc ) ^~ ; generating N AoDs and N AoAs for N transmitter side clusters and N receiver side clusters, respectively, from distributions p _c ^T {0) and ρ (θ) , respectively; and pairing them randomly to obtain N pairs of Tx-Rx clusters that form N paths of the multipath channel.

[0022]

The method used for a mobile communications system may further comprise:

assuming the same distributions for AoA and AoD. f

11

[0023]

The L AoD offsets and M AoA offsets may be predefined according to distribution p _s (9 _s ) , and may be used for all paths without generating AoA and AoD offsets for each path.

[0024]

The channel gain may be expressed as

where L is a number of scatterers per Tx-cluster,

M is a number of scatterers per Rx-cluster,

^Vj¾ is a velocity of the transmitter,

^Yrx is a velocity of the receiver,

Θ jth nj.AoD [ _{s m} angle ₀ f departure (AoD) of a ray from a transmitter to ' Tx-scatterer ' located m an " Tx-cluster,

6 _n ,m,AoA j _s an angle ₀ f arrival (AoA) of a ray from ^m ' ^h Rx-scatterer ^ ^m located th

in an ⁿ Rx-cluster to a receiver, t is time,

Q _n ,i,m j _{s a} phase shift due to l' ^h Tx-scatterer located in the ⁿ ' ^h Tx-cluster and ^m ' ^h Rx-scatterer ^ ^m located in the ⁿ ' ^h Rx-cluster, ψη ^, ι,π, j _{s a} phase shift due to a path length from Tx-to- ' -to- ^m -to-Rx, k - ^27C

* is a wave number and has a value of A ₅ Λ being a wavelength, G (Θ )

. n,i,AoD g _a transmitter antenna gain of each array element, G (Θ 1

Rx \ n,m,AoA ) j _{g a reC} eiver antenna gain of each array element, ση,5Ρ jg _{a sna(} jow fading factor for ⁿ ' ^h path, and Φ Φ

" ^■ ' and " ^> " ^■ are single valuables that represent Θ _η ,ι + ψη,ι and #„, _m + (p„ _im + ψη, respectively, and are assumed to be uniformly distributed over [ ^~π ' ^π ) ,

φ _η ,ι -kd _nj , d _{n l} being a distance between a transmitter and ' Tx-scatterer

' located in the ⁿ Tx-cluster,

(Pn,m ^~ kd% _m , d _m being a distance between a receiver and ^m ' Rx-scatterer

th

m located in the ⁿ Rx-cluster, and is a phase shift due to distance between the ⁿ -th Tx-cluster and the ⁿ -th Rx-cluster.

[0025]

The method used for a mobile communications system may further comprise: generating AoD ^"- ^AoD of the ⁿ ' ^h transmit cluster and AoA ® ⁿ < ^AoA from the receive cluster independently from distributions ^ ^c ^ and ^ ^c ^ , respectively; generating ^L AoD offsets ( ^ ^{l>AoD 1} ' ^" ' ⁱ ) of the ⁿ ' ^h Tx cluster and ^M AoA

Δ m = 1,.., M , _h

offsets ( ^m>A0A ) of the ⁿ Rx cluster independently from distribution of scatterers within a cluster obtaining ^L AoDs ( ⁿ - ^l > ^AoD ) M AoAs ( ^» . ^m - ^AoA ) using &n,m,AoA ⁼ &n,AoA + ^m,AoA > generating phase changes Φ _{η 1} ,1 = \,...,L and _{n m} ,m = \,...,M independently from a uniform distribution over [-π, π) .

[0026]

θ θ

AoD "-^, ΑοΑ ⁿ - ^AoA , the ^L AoD offsets, the ^M AoA offsets, and the phase changes may be generated using random values.

[0027] The method used for a mobile communications system may further comprise: assuming symmetric distributions for AoD and AoA such that ^ ^c ^ ^~ ^ ^c ^ ^_ ^ ^c ^ ^' , generating N AoDs and N AoAs for N transmitter side clusters and N receiver side clusters, respectively, from distributions p _c ^T {9) and ρ (θ) , respectively; and pairing them randomly to obtain N pairs of Tx-Rx clusters that form N paths of the multipath channel.

[0028]

The method used for a mobile communications system may further comprise: assuming the same distributions for AoA and AoD. [0029]

The L AoD offsets and M AoA offsets may be predefined according to distribution p _s (0 _S ) , and are used for all paths without generating AoA and AoD offsets for each path.

[0030]

In a second form, the present invention relates broadly to a user equipment used in a mobile communications system, wherein the user equipment is designed by obtaining a channel gain according to values for power of an ⁿ path " , a direction of Tx motion ^Tx , a spacing between antenna elements at a transmitter and a reference transmitter antenna ^T , a direction of

Rx motion ^¾ , and a spacing between antenna elements at a receiver and a reference receiver antenna R .

[0031]

In a third form, the present invention relates broadly to a simulator used for a mobile communications system, the simulator including:

a computer configured to obtain a channel gain according to values for power of an ⁿ ' ^h

P 9 ^V

path " , a direction of Tx motion ^Tx , a spacing between antenna elements at a transmitter and a reference transmitter antenna τ _? a direction of Rx motion ^¾ , and a spacing between antenna elements at a receiver and a reference receiver antenna « . [0032]

Any of the features or aspects of any form of the invention described herein can be combined in any combination with any one or more other features or aspects of any form of the invention described herein.

Advantageous Effects of Invention

[0033]

According to the present invention, it is possible to provide a channel model that is simple but sufficiently appropriate for the purpose of generating accurate channel coefficients.

Brief Description of Drawings

[0034]

Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

[Fig- 1]

Fig. 1 is a schematic representation of a related double-ring scattering model for a single-input-single-output (SISO) channel.

[Fig. 2]

Fig. 2 is a schematic representation of a related double-ring scattering model for a multiple-input-multiple-output (MIMO) channel.

[Fig- 3]

Fig. 3 is a schematic representation of a double-ring scattering model for a MIMO multipath fading device-to-device (D2D) channel.

[Fig- 4]

Fig. 4 is a schematic representation of a simplified double-ring scattering model for a MIMO multipath fading D2D channel.

Description of Embodiments

[0035]

It is useful to first explain the derivation of a low complexity multipath spatial model which may be used in D2D communication channel simulation. For this purpose, to begin with, a "reference D2D channel model" (300) representing a multipath MIMO channel between two D2D devices is defined and illustrated in Fig. 3.

[0036]

The model (300) in Fig. 3 is based on the 'double-ring scattering model for a MIMO channel' (200) described in the Background section above. Also, in Fig. 3, a single path channel environment is represented by a single path (304) arriving at the receiver antenna with a delay. There is a pair of scatterer clusters, the pair comprising a transmit-scatterer-cluster (303.a) located in the Tx-scatterer-ring (302. a) and a receive-scatterer-cluster (303.b) located in the Rx-scatterer-ring (302.b).

[0037]

The multipath channel environment is represented by N paths arriving at the receive antenna with different delays. There are N paths as there are N pairs of

transmit-scatterer-clusters (303.a) and receive-scatterer-clusters (303.b) located in the

Tx-scatterer-ring (302.a) and Rx-scatterer-ring (302.b) respectively. The ⁿ -th path is therefore an aggregation of waves scattered around a cluster of transmitter scatterers and a cluster of receiver scatterers.

[0038]

Importantly, in the reference D2D channel model (300), it is again assumed that there are infinite scatterers per cluster, that is, in the transmit-scatterer-clusters (303.a) and in the receive-scatterer-clusters (303.b). Due to symmetry of the environment around the transmitter (301. a) and receiver (301.b), the distribution of the clusters of scatterers around the transmitter, denoted ^ ^c ^ , may be assumed to be the same as the distribution of the clusters of scatterers around the receiver, denoted ^ ^c ^ . This gives the distribution of AoDs (306.a) and AoAs (306.b) per cluster. The distribution of scatterers within a given cluster is represented by gives the distribution of AoDs (307. a) and AoAs (307.b) of each ray within a cluster. Due to the assumption of infinite scatterers within each transmitter-scatterer-cluster (303.a) and receiver-scatterer-cluster (303.b), there are infinite rays (308) that form the ⁿ -th path as illustrated in the model (300). Accordingly, the channel coefficient ^".".^ representing the 'reference model' for the D2D communication channel of the ^n>h path between the ^s ' ^h transmit antenna and the ^u ' ^h receive antenna can be obtained by applying the following formula: exp[/(* ll ν _Λ || cos(^ _o0 -^)t +^ || .ν _Λ l| cos(¾^ -¾)f -^^]x exp[/£(£; sin(6>„^ _oD ) + <¾ sin(^ ₀ )]x exp[/¾, J

Equation 5

Where represents the scatterers per Tx cluster (303. a),

M represents the scatterers per Rx-cluster (303.b),

P„ is the power of the n ^th path,

\ _Tx is the velocity of the transmitter (301.a),

v _¾ is the velocity of the receiver (301.b),

0 _χ is the direction of the transmitter (301.a) motion w.r.t. the transmitter broadside, is the direction of the receiver (301.b) motion w.r.t. the receiver broadside, @n,t,AoD i ^{s me} AoD of the ray from the transmitter (301.a) to the I ^th Tx-scatterer TS, (303. La) located in the n' ^h Tx-scatterer-cluster (303. a),

θ _η ,π,,ΑοΑ is the AoA of the ray from the m' ^h Rx-scatterer &S ^, _m (303.m.b) located in the n' ^h Rx-scatterer-cluster (303.b) to the receiver (301.b),

θ _{η 1 ηι} is the phase shift due to /'* Tx-scatterer TS _l (303. La) located in the n' ^h Tx-scatterer-cluster (303.a) and the m' ^h Rx-scatterer RS _m (303.m.b) located in the n' ^h Rx-scatterer-cluster (303. b),

<p _{n ! m} is the phase shift due to path length from Tx (301.a)-to- S _/ -to- RS _m -to-Rx (301.b),

k is the wave number and has value of t =— , and λ is the wave length,

λ

δγ is the spacing between transmitter antenna element s and the reference transmitter antenna element, and

δ is the spacing between receiver antenna element u and the reference receiver antenna element (The spacing between the two transmit antennas is δ _τ (305. a) and the spacing between the two receive antennas is S _R (305.b).).

[0039] An approximation of the above-described "reference D2D channel model" (300) may be used as a "generalised stochastic model", and whereas the "reference D2D channel model" (300) assumed infinite scatterers per cluster, the approximation which may be used as a "generalised stochastic model" assumes a finite number of scatterers per Tx cluster (303.a) and Rx cluster (303.b). Accordingly, the channel coefficient h _{n u s} (t) representing the generalised stochastic model for the D2D communication channel of the n' ^h path between the s' ^h transmit antenna and the u' ^h receive antenna can be obtained by applying the following formula: Equation 6

Where:

• L is the finite number of scatterers per Tx-cluster (303. a) and

• M is the finite number of scatterers per Rx-cluster (303. b).

Note that the number of scatterers per Tx-cluster (or Rx-cluster) is assumed to be the same across all paths.

[0040]

The "generalised stochastic model" represented in Equation 6 (which, it will be recalled, is an approximation of the reference model in Equation 5 based on a finite number of scatterers per cluster) does not consider shadow fading and considers omni-directional antennas with a gain of 1 (i.e. unit gain) at both the transmitter and the receiver. Shadow fading per path and antenna gains (i.e. non-unit gains) for specific antenna designs at both ends can be incorporated into the model as follows:

Equation 6a

Where

· G _Tx (6 _{n l AoD} ) is the transmitter antenna gain of each array element,

• GRx ( n,m,AoA ) is ^me receiver antenna gain of each array element, and

• σ _{η 5Ρ} is the shadow fading factor for n' ^h path.

[0041]

The normalised spatial-temporal correlation function expressed by can be averaged over phase shifts due to Tx and Rx scatterers

Θ (p

n . _? phase shifts due to path length ⁿ ' ^m and N paths, and expectations can be taken over

AoAs and AoDs with E{exp(j(<P _n , _m -<P _n ,rJ} = 0 _{for l≠V} and m≠m to obtain a normalised spatial-temporal correlation function ^2¾^^'^^«' ^r ) using the following formula:

= -^ £{exp ^'Mi ^ sin((„ _4oD )) x exp(- _. /l || v _a || cos(<9„ _oD - θ _Τ ^ν _χ )τ)}>

M TE{expO A<¾ sm(0 _{n<m AoA} ))xexp(-jk \\ v _¾ || cos{9 _{n m AoA} -θ^τ)) Equation 7

[0042]

Next, spatial Cross Correlation Functions (CCF), (Δδ , Δ<¾ ) _{t ¾¾} (AS _j ) and P _Ulu2 (Δ<¾ _? ) can be obtained by using the formulae:

1 L ^M

ρ (Αδϊ,Αδ _Λ ") =— -∑E{exp ^ sin(^ _;UoO ))}∑E{exp ¾" ύη{θ _η ^ _ΑοΑ ))}

E uation 8a

Equation 8b

1 iw

P _* u _u , _l u _U22 (Δ¾ K /) =—∑E{ex _P ( A¾ sinfl^))}

M m=l

Equation 8c

/¾£ (Δ^; , Δ<¾ ) = _¾ (Δ^ )p _UiUi (Αδ ^« )

Equation 8d

[0043]

The temporal auto correlation function (ACF) p (r) can be obtained by using the followin formula:

P = -<¾»}

Equation 9

[0044]

The "generalised stochastic model" discussed above may be further simplified to give a

"simplified stochastic model" that involves less computational complexity. Simplification of the "generalised stochastic model" to give the "simplified stochastic model" may rely on the fact (or the assumption) that the scatterers (303.1. a to 303.1.a) in the Tx-cluster (303. a) are located close enough, and that the scatterers (303. l.b to 303.m.b) in the Rx-cluster (303.b) are located close enough, to consider that the phase shift caused by the Rx-scatterer RS _m (303. m.b) due to a wave received from the Tx-scatterer TS _t (303. La) is approximately equal to the phase shift caused by the same Rx-scatterer due to a wave received from the Tx-scatterer TS _r ,l'≠ I . This implies that the phase shifts caused by the Tx-scatterers (303.1. a to 303.1.a) in the Tx-cluster (303.a) are independent of the Rx-scatterers (303. l.b to 303.m.b) in the Rx-cluster (303.b), and vice versa. Thus

Equation 10

Where

• Q _n i is the phase shift due to ^ Tx-scatterer located in the ⁿ ' ^h Tx-cluster, and

• θ _{η τη} is the phase shift due to ^m ' ^h Rx-scatterer ^ ^m located in the ⁿ ' ^h

Rx-cluster.

[0045]

The phase shift due to the total path length of a particular multi-path from transmitter to receiver may also be expressed as:

exp[/> _{n /;} J = exp[/*(¾ + <¾, + j]

Equation 11

Where

• d¾3 is distance from the transmitter (301. a) to the I ^th Tx-scatterer TS _l (303.1.a) located in the n' ^h Tx-scatterer-cluster (303. a), and _d RS

un,m is distance from the m' ^h Rx-scatterer RS _m (303. m.b) located

Rx-scatterer-cluster (303.b) to the receiver (301.b).

[0046]

L M

And hence, the summation exp[yiP,, _{/ m} ] may be expressed as

L M L M

∑∑ exp[j ⁽ p _Mj . J =∑∑ exp[jk(d™ + d? _m + d _m )]

1=1 m=l /=1 m=l

Equation 12

[0047]

Considering the fact (or the assumption) that the scatterers (303. l.a to 303.1.a or 303. l.b to 303.m.b) vsdthin a cluster are closely located, the distance d" _m between Tx-scatterer TS _l (303. l.a) and Rx-scatterer RS _m (303.m.b) may be expressed as d" = d" +A,

Equation 13

Where

• d" is the distance between the « -th Tx-cluster (303. a) and the « -th Rx-cluster (303. b).

[0048]

And using the first order Maclaurin series approximation, the expression exp[jkd" _m ] may be simplified as

exp[/¾] = exp{Jk(d ⁿ +A _{l m} )] = exp{jkd ⁿ ].exp{JkA _{! m} ] « Qxp{Jkd ⁿ ][l+ jkA _{l m} ].

Equation 14

[0049]

Using Equations 14, the summation in Equation 12 can be re-written as: + ...

]

Equation 15

[0050]

Equation 15 can be further approximated by neglecting the contribution from small distances Δ, _m as follows.

expC , _m )

Equation 16

Where

• ψη,ι , being the distance between the transmitter and Tx-scatterer

' located in the ⁿ Tx-cluster, and

• <Pn,m~kdn _m , being the distance between the receiver and ' ^h Rx-scatterer m located in the ⁿ Rx-cluster.

[0051]

The simplified stochastic model may be obtained from Equation 10 and Equation 16 as follows:

Equation 17

Where • φ _η is the phase due to the distance d" .

[0052]

The random phase change due to scatterers and the path length at each end may be represented by a single variable as:

n,m n,m < n n,m

Equation 18

with Φ _η , and Φ _{π m} assumed to be uniformly distributed over [-π, π) to obtain the simplified stochastic model for spatial D2D channel as: = ^(∑ ^expL/'(A; ll ^v ^i ^cos( ^ ^8ίη (^) ^{+ φ} , )]) ^χ

f M

∑exp[y ^||v _¾ ||cos(^ _m ^ - ^)t + ," sin(^ ₀ J + 0„ _>m )]

m=l

Equation 19

[0053]

The simplified stochastic model may be further generalised to include shadow fading effect and

Equation 20

Where

· G _Tx (θ _{η Ι ΑοΌ} ) is the transmitter antenna gain of each antenna element,

• ^ίΐχ Ψη,τη,ΑοΑ is the receiver antenna gain of each antenna element, and

• σ _{η ;iSF} is the shadow fading factor for n' ^h path.

[0054]

The model represented by Equation 19 (or Equation 20) may be interpreted in the manner illustrated in Fig. 4. Fig. 4 shows a model (400), and in Fig. 4, a cluster of

Tx-scatterers (403. a) located in the Tx-scatterer-ring (402. a) is interpreted as (i.e. it is modelled to operate effectively as) a "virtual-transmitter" so that the aggregation of power received at all scatterers in the ⁿ ' ^h Tx-cluster (403. a) is reached at the ⁿ ' ^h Rx-cluster (403. b) as a single wave (404). c¾ is distance from the transmitter (401. a) to the l' ^h Tx-scatterer TS _t located in the cluster of Tx-scatterers (403. a), and d^ is distance from the m ^th Rx-scatterer RS _m located in the cluster of Rx-scatterers (403.b) to the receiver (401.b).

[0055]

The simplified stochastic model discussed above may be put to a range of uses. As one example, it may be used to provide a method for calculating channel coefficients, for instance, in D2D system level simulations. More specifically, according to this example, a method for calculating channel coefficients for the n ^th path between a transmit antenna s and a receive antenna ^u may comprise the following:

1. Assuming or assigning known values for variables including the power of the n' ^h path P _n , the direction of Tx motion θ _Τ ^ν _χ (and the velocity), the spacing between antenna elements at the transmitter and the reference transmitter antenna S _T ^S , the direction of Rx motion ff^ (and the velocity), and the spacing between antenna elements at the receiver and the reference receiver antenna δ . Note that assuming or assigning values to such variables could perhaps be viewed as optional, but if values are not assigned, channel coefficients obtained using the method will be expressed as a function of the unknown variables rather than explicitly.

2. Generating, for example using random values, the AoD ^ ⁿ > ^AoD of the ⁿ ' ^h transmit

Θ th

scatterer cluster and the AoA "· ^ΑοΛ from the ⁿ receive scatterer cluster independently from the distributions ^ ^c ^ and ? ^c ^ respectively. For the purposes of this step, symmetric distributions for AoD and AoA may be assumed such that ^(^) - Pc (^) - -Pc(^) . preferably N AoDs and N AoAs for N transmitter side clusters and N receiver side clusters respectively can be generated from the distributions p _c ^T (Θ) and ρ (θ) , respectively, and pair them randomly to obtain N pairs of Tx-Rx clusters that form N paths of the multipath channel.

3. Generating, for example using random values, L AoD offsets (

) of the Tx cluster and ^M AoA offsets ( ^" ^>AoA '™ ^~ ^-' ^M ) of the "

Rx-cluster independently from the distribution of scatterers within a cluster Note that both step 2 and step 3 may assume the same distributions for AoA and AoD (i.e. a symmetric AoA and AoD scenario). Preferably, the L AoD offsets and M AoA offsets could be predefined according to the distribution p _s (0 _S ) , and could be used for all paths, without generating AoA and AoD offsets for each path on the fly. Further, the values of L and M could be the same or different.

θ Θ

4. Obtaining ^L AoDs ( "•' ^■,oD ) and M AoAs ( ⁿ > ^m < ^AoA ) \x%m

n ,l,AoD ~ n ,AoD ⁺ ^ I,AoD

n _ n

n,m ,AoA η ,ΑοΑ τη ,ΑοΑ

5. Generating phase changes _{η 1} ,1 = \,...,L and Φ„ _m ,m = \,...,M independently, for example using random values, from a uniform distribution over [-π, π) .

6. Generating the channel coefficient h _{n u s} (t) at time instant t using Equation 19 (or

Equation 20 if antenna gains of the transmitter elements and receiver elements are known).

[0056]

As mentioned above, the simplified stochastic model discussed above may be put to a range of uses. The same applies for the generalised stochastic model. One example use is explained above. As another example, the simplified stochastic model or the generalised stochastic model may provide a means for generating a 'spatial channel correlation matrix' for a path n , or a common spatial correlation matrix for all paths. This may be useful, for example, in link level performance evaluation simulation for assessing technologies appropriate for D2D communication.

[0057]

Firstly, 'spatial cross correlation functions' (CCFs) for Transmitter-Receiver (Tx-Rx), transmitter (Tx), and receiver (Rx) are required. According to the "simplified stochastic model' and the "generalised stochastic model" discussed above:

a. the s atial CCF for Tx-Rx is (Equation 8a)

))} ,

and c. the spatial CCF for Rx is (Equation 8c) p _m (AS _R ^U )

[0058]

Due to the separability property, the CCF for Tx-Rx can be written as (Equation 8d) Ps£ (^ _T > ^AS R ) = A _1¾ ( ^AS T )P _{U U2} ( ^Δ <¾) , and this can be further simplified to 5 ^ r p s ^S ₂ ^lU u ^l ₂ = p s ^T _t ^x s ₂ .p r u _x ^* u .

[0059]

Since

• p^ is an element of the spatial cross correlation matrix at the transmitter R _X for a path n ,

0 · ^' is an element of the spatial cross correlation matrix at the receiver R^ for a path n , and

• p^ is an element of the D2D spatial cross correlation matrix R _D " _{2D spatia} i for a path n ,

it follows that the D2D spatial cross correlation matrix R _D ⁿ ₂ D, _S pauai f° ^{r a} P ^{am n w} iU ^ ^{e me} 5 Kronecker product ' ® Of R" _X and R^ . Thus, R _D ^N _2D,SPATIAL = R _T " _X ® R^ .

[0060]

E\ }

A common spatial correlation matrix for all paths may be obtained as the average ¹ '

correlation matrix over all paths, hence

[0061]

0 Assuming symmetric scatterer distributions around the transmitter and the receiver (and hence symmetric AoA and AoD distributions), a base correlation matrix for two anten elements at the transmitter or the receiver may be defined as R _TX = i? _¾ = R DID UE

The elements of this matrix may be generated by

A. simulating N x L random AoA/ AoD {θ _{η Ι ΑοϋΙΑοΑ} ) values. It will be recalled that the

Q

generation of the AoD of the n ^th Tx cluster ( ⁿ ' ^AoD ) and the AoA of the n ^th Rx cluster g

( ^» . ^A ° ^A ) is explained as step 2 of the method for calculating channel coefficients above.

Also, the generation of the AoD offsets and AoA offsets is explained as step 3 of that method. Furthermore, the calculation of the AoDs ( ^nJ - ^AoD ) and AoAs ( ⁿ ' ^m - ^AoA ) is explained as step 4 of that method. Hence, the N x L random Ao A/AoD ( 0 _{n) AoDIAoA} ) values here may be

θ Θ

determined from the AoDs ( " ^J - ^AoD ) and AoAs ( " ^■ '" ^■AoA ) for all paths n (n = l ... N).

B. determining the elements ( P ) of the base correlation matrices from sample averaging as

N L

AoDIAoA

T ))

n=\ 1=1

Where: Ad is the normalised distance between two antenna elements of Tx or Rx, k is a wave number given by k = ^ and λ is the transmission wavelength.

A.

[0062]

Correlation matrices for 'medium' and 'high' correlation may also prove useful for simplified link level simulations.

i. In relation to "medium" correlation, combining the fact that transmitting (and receiving) D2D_UEs are surrounded by a rich scattering environment (such as urban Hotspots) giving larger angular spreads per path, per cluster (e.g. >60°) at the transmitter (and the receiver) which results in low correlations between received signals at different antenna elements, and the fact that a typical antenna spacing of A / 2 (half of a wavelength) at the D2D_UE results in high correlations between received signals at different antenna elements, a sensible value for the 'medium' correlation coefficient may be 0.1 <

Pmedium < OA, and most preferably p _medium = 0.25 . As a result, exemplary correlation matrices for medium correlation may be given by

1 2 case medium Pmedium 1 0.25

R D2D,spatial

medium 1 0.25 1

2 x 2 case

medium Pmedium ²

R DID, patial ®

1 medium

1 0.25 0.25 0.0625

medium 0.25 1 0.0625 0.25

R D2D,spatial

0.25 0.0625 1 0.25

0.0625 0.25 0.25 1 ii. In relation to "high" correlation, considering that an open environment with less scattering surfaces around a D2D_UE results in low angular spreads (e.g. <35°) per path with typical antenna spacing of (half a wavelength) at a D2D UE resulting in high correlations between received signals at different antenna elements, a sensible value for a 'high' correlation coefficient may be 0.7 < p _me dium < 0-9, and most preferably ^ ^high . Note that correlations as high as 0.9 may not be possible at a UE due to low antenna heights and relatively large angular spreads at a D2D_UE compared with a cellular base station. In any case, based on a 'high' correlation coefficient value of ^ ^high , exem lary correlation matrices for high correlation may be given by

1 x 2 case nhigh

l D2D,spalial

2 x2 case Phigh Phigh Phigh

* 2 medium ¹ Phigh 1 Phigh Phigh 1 Phigh Phigh

R DID, spatial ⁽ 8> * 2

/high ¹ /high ¹ Phigh Phigh 1 Phigh iPhiglt ) Phigh Phigh ^

1 0.8 0.8 0.64

medium 0.8 1 0.64 0.8

R D2D,spatial

0.8 0.64 1 0.8

0.64 0.8 0.28 1 [0063]

In the present specification and claims (if any), the word 'comprising' and its derivatives including 'comprises' and 'comprise' include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0064]

In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any)

appropriately interpreted by those skilled in the art.

[0065] For example, the present invention can be implemented in the following forms.

[0066]

(1) A computer implemented simulator operable to calculate a channel coefficient ( _{n u s} (t) ) for a simulated wireless transmission path (n) from a moving transmit antenna(s) (s) to a moving receive antenna(s) (u), the transmission path including a cluster of transmit scatterers associated with the transmit antenna and a cluster of receive scatterers associated with the receive antenna, the computer implemented simulator implementing the steps of:

Q

• generating an angle of departure ( °° ) of the path from the transmit antenna to the

Q

cluster of transmit scatterers, and generating an angle of arrival ( "- ^AoA ) of the path at the receive antenna from the cluster of receive scatterers;

• generating an angle of departure offset f r ° ⁿ e ^or more individual transmit scatterers within the cluster of transmit scatterers, and generating an angle of arrival offset (A _{M AOA} ) for one or more individual receive scatterers within the cluster of receive scatterers;

Q

• using the angle of departure ( - ^AoD ) and the one or more angle of departure offsets

Q

(AI,A _O D) to calculate one or more individual angles of departure ( " ^<l ' ^AoD ) of the path from the transmit antenna to the one or more respective individual transmit scatterers,

Θ

and using the angle of arrival ( ^» · ^ΑοΛ ) and the one or more angle of arrival offsets

Q

(Δ _Τ Π,Α _Ο Α) to calculate one or more individual angles of arrival ( ⁿ - ^m ' ^AoA ) of the path at the receive antenna from the respective one or more individual receive scatterers; and

• calculating the channel coefficient ( h _{n u s} (t) ) using the one or more individual angles of θ Θ departure ( "·'· ^Αο ° ) and the one or more individual angles of arrival ( ^η ·'"· ^ΑοΑ ).

[0067]

As explained above, the first broad form of the invention relates to a simulator which is computer implemented. A wide range of different forms of computer implementation are possible and all are considered to fall within the scope of the present invention. Hence, the invention in the first broad form is in no way restricted to any particular form of computer implementation. By way of example, the simulator could be implemented on a general purpose computer (e.g. a personal computer (PC) or notebook, etc). Alternatively, the simulator may be implemented using purpose-built computer hardware. In any case, the computer (or computer hardware) on which the simulator in this form of the invention is implemented will generally include a processor, memory and a user interface for enabling a user to interact with the computer. The user interface could include, for example, a display (e.g. a computer screen), a keyboard, a mouse and the like. Other input means may also be provided such as vocal input means, data input means (e.g. a USB or ethernet port, a WiFi, Bluetooth or other wireless connection, or a media reader like a CD/DVD or memory card reader), etc.

[0068]

Therefore, a user may be able to use the computer implemented simulator when performing testing and/or design work relating to wireless communication technologies to quickly and easily calculate channel coefficients which may be relevant to the assessment of the technology under consideration. An advantage of the computer implemented simulator in the first form of the invention may also lie in the fact that calculation of the channel coefficients may involve a relatively low computation burden (i.e. a relatively small amount of

"number-crunching" may be required).

[0069]

(2) The computer implemented simulator as claimed in Item 1 further operable to generate one or more phase changes (Φ _η> 2 , Φ _η, τη) ^{to use} the ^{one or} more phase changes in calculating the channel coefficient ( h _{n u s} (t) ).

(3) The computer implemented simulator as claimed in Item 2 wherein one or more of the θ Θ

angle of departure ( ⁿ - ^AoD ), angle of arrival ( ⁿ - ^AoA ), angle of departure offset(s) (Δ^ _ο£) ), angle of arrival offset(s) (& _{m AoA} ) and phase change(s) (Φ _{η ί} , _n<m ) are randomly generated.

(4) The computer implemented simulator as claimed in Item 3 wherein the one or more

phase changes are randomly generated independently from a uniform distribution over

[-π,π) .

(5) The computer implemented simulator as claimed in Item 1 wherein the cluster of transmit scatterers comprises a first finite number of transmit scatterers (L) and the cluster of receive scatterers comprises a second finite number of receive scatterers (M), the first finite number (L) and the second finite number (M) being the same or different.

(6) The computer implemented simulator as claimed in Item 5 wherein an angle of departure offset ( I AOD) is generated for all (L) of the individual transmit scatterers within the cluster of transmit scatterers, and an angle of arrival offset (ΔΤΠ,ΑΟΑ) is generated for all (M) of the individual receive scatterers within the cluster of receive scatterers.

(7) The computer implemented simulator as claimed in Item 6 wherein the (L) angle of

departure offset(s) and ^tne ( ) angle of arrival offset(s) (A _{m AoA} ) are predefined and can be used for calculating the channel coefficient ( h _{n u s} (t) ) for different paths without needing to be generated for each path.

(8) The computer implemented simulator as claimed in Item 7 wherein an individual angle of

Q

departure ( ⁿ - ^l - ^AoD ) of the path from the transmit antenna to an individual transmit

Q

scatterer (I) is calculated as the sum of the angle of departure ( "- ^AoD ) and the angle of departure offset (A _{i i4o} ) for that individual transmit scatterer (I) (i.e.

(9) The computer implemented simulator as claimed in Item 8 wherein an individual angle of

Q

arrival ( "- ^m - ^AoA ) of the path at the receive antenna from an individual receive scatterer g

(m) is calculated as the sum of the angle of arrival ( "· ^ΑοΑ ) and the angle of arrival offset (Δ _Τ Π,Α _Ο Α) for that individual receive scatterer (m) (i.e. θ _{η ηι ΑοΑ} = θ _{η ΑοΑ} + A _{m AoA} ).

(10) The computer implemented simulator as claimed in Item 9 wherein the transmit antenna is one of two transmit antennas separated by a transmitter spacing (5 ) and the receive antenna is one of two receive antennas separated by a receiver spacing (<¾), and the computer implemented simulator is further operable to assign values for the transmitter spacing (δγ), receiver spacing (<5# ), power (P _n ) of the path (n), velocity ( ^ν¾ ) and

Q ^v v θ ^ν

direction ( ^Tx ) of the transmit antenna, velocity ( ^¾ ) and direction ( ^Rx ) of the receive

27Γ

antenna, and the transmission wavelength (Λ) (or the wave number k =— ).

A.

(1 1) The computer implemented simulator as claimed in Item 10 being further operable to calculate the channel coefficient ( h _{n u s} (t) ) for time t using the formula:

(12) The computer implemented simulator as claimed in Item 11 wherein there is an antenna gain ( G _TX (9 _{N L AOD} ) ) associated with each transmit antenna and there is an antenna gain ( ^Rx (^n,m,AoA ) associated with each receive antenna, and there is a shadow fading factor

^ ^a n,sF -j associated with each path, and the computer implemented simulator is further operable to calculate the channel coefficient ( h _{n u s} (t) ) for time t using the formula:

SF

∑ τλθ _η, ι,Αοο) expD ^' (fc| _r Jcos(0„ _iUoZ5 - 0 _T ^v _x )t + kS _T ' s (e _{n l AoD} ) + Φ„ ,)]

L

(13) A method for calculating a channel coefficient ( h _{n u s} (t) ) for a simulated wireless

transmission path (n) from a moving transmit antenna(s) (s) to a moving receive antenna(s) (it), the transmission path including a cluster of transmit scatterers associated with the transmit antenna and a cluster of receive scatterers associated with the receive antenna, the method comprising:

Q

generating an angle of departure ( " ^>AoD ) of the path from the transmit antenna to the cluster

Q

of transmit scatterers, and generating an angle of arrival ( "· ^ΑοΑ ) of the path at the receive antenna from the cluster of receive scatterers;

generating an angle of departure offset for one or more individual transmit scatterers within the cluster of transmit scatterers, and generating an angle of arrival offset (A _{m AoA} ) for one or more individual receive scatterers within the cluster of receive scatterers;

Q

using the angle of departure ( ^η - ^ΑοΌ ) and the one or more angle of departure offsets (A _{i i4oD} ) ø

to calculate one or more individual angles of departure ( " ^J - ^AoD ) of the path from the transmit antenna to the one or more respective individual transmit scatterers, and using the ø

angle of arrival ( "· ^ΑοΑ ) and the one or more angle of arrival offsets (A _{m AoA} ) to calculate one ø

or more individual angles of arrival ( " ^<m - ^AoA ) of the path at the receive antenna from the respective one or more individual receive scatterers; and

calculating the channel coefficient { h _{n u s} {t) ) using the one or more individual angles of ø ø

departure ( ' ^AoD ) and the one or more individual angles of arrival ( ^η ·" ^> > ^ΑοΑ ).

(14) The method as claimed in Item 13 further including generating one or more phase

changes (Φ _{η ί} , Φ _η<τη ) and using the one or more phase changes in calculating the channel coefficient ( h _{n u s} (t) ). (15) The method as claimed in Item 14 wherein one or more of the angle of departure θ Θ

( "- ^AoD ), angle of arrival ( "· ^ΑοΑ ), angle of departure offset(s) (Aj _AoD ), angle of arrival offset(s) (& _{m AoA} ) phase change(s) (Φ _ηι ι, Φ _η ,πι) are randomly generated.

(16) The method as claimed in Item 15 wherein the one or more phase changes are randomly generated independently from a uniform distribution over [-π, π) .

(17) The method as claimed in Item 13 wherein the cluster of transmit scatterers comprises a first finite number of transmit scatterers (L) and the cluster of receive scatterers comprises a second finite number of receive scatterers ( ), the first finite number (L) and the second finite number (M) being the same or different.

(18) The method as claimed in Item 17 wherein an angle of departure offset (&i _AoD ) is

generated for all (L) of the individual transmit scatterers within the cluster of transmit scatterers, and an angle of arrival offset (& _{m AoA} ) is generated for all (M) of the individual receive scatterers within the cluster of receive scatterers.

(19) The method as claimed in Item 18 wherein the (L) angle of departure offset(s) ( _{l AoD} ) and the (M) angle of arrival offset(s) (A _{m AoA} ) are predefined and can be used for calculating the channel coefficient ( h _{n u s} (t) ) for different paths without needing to be generated for each path.

g

(20) The method as claimed in Item 19 wherein an individual angle of departure ( " ^>l ' ^AoD ) of the path from the transmit antenna to an individual transmit scatterer (I) is calculated as the sum of the angle of departure ( for that individual transmit scatterer (I) (i.e. θ _{η Ι ΑοΩ} = θ _{η ά0θ} + A _{l AoD} ).

Q

(21) The method as claimed in Item 20 wherein an individual angle of arrival ( "< ^m - ^AoA ) of the path at the receive antenna from an individual receive scatterer (m) is calculated as the

g

sum of the angle of arrival ( ^η · ^ΑοΛ ) and the angle of arrival offset (A _{m AoA} ) for that individual receive scatterer (m) (i.e. θ _{η ίη ΑοΑ} = θ _{η ΑοΑ} + A _{m AoA} ).

(22) The method as claimed in Item 21 wherein the transmit antenna is one of two transmit antennas separated by a transmitter spacing (δγ) and the receive antenna is one of two receive antennas separated by a receiver spacing (δ%), the method further include assigning values to the transmitter spacing (δγ), receiver spacing (δ% ), power (P _n ) of the v θ ^ν v path (n), velocity ( ^Tx ) and direction ( ^Tx ) of the transmit antenna, velocity ( ^¾ ) and θ ^ν

direction ( ^¾ ) of the receive antenna, and the transmission wavelength (A) (or the wave number k = ~).

A.

(23) The method as claimed in Item 22 further comprising calculating the channel coefficient ( K u s ( ) f° ^r ti ^me * using the formula:

(24) The method as claimed in Item 23 wherein there is an antenna gain ( G _Tx (θ _η , _AoD ) ) associated with each transmit antenna and there is an antenna gain ( G _Rx (0 _{n m AoA} ) ) associated with each receive antenna, and there is a shadow fading factor ( ^<7 "" ^SF ) associated with each path, and the method further comprises calculating the channel coefficient ( h _{n u s} (t) ) for time t using the formula: »,s «) = x .

(25) A method for generating a spatial channel correlation matrix (RjD2D,spatiai) f° ^{r a}

simulated wireless transmission path (n) from a moving transmit antenna(s) of a transmitter to a moving receive antenna(s) of a receiver, wherein the transmission path includes a cluster of transmit scatterers associated with the transmit antenna and a cluster of receive scatterers associated with the receive antenna, the method comprising generating the spatial channel correlation matrix (R£ ₂ o, spatial) f° ^{r me} P ^am fr° ^{m me} Kronecker product of a spatial cross correlation matrix for the path at the transmitter (RT _X ) and a spatial cross correlation matrix for the path at the receiver (RR _X ) (i.e.

(26) A method for generating a common spatial channel correlation matrix (Ro2D,spatiai) f° ^r a number (N) of simulated wireless transmission paths (n = 1 ... N) from a moving transmit antenna(s) of a transmitter to a moving receive antenna(s) of a receiver, wherein each transmission path includes a cluster of (L) transmit scatterers associated with the transmit antenna and a cluster of ( ) receive scatterers associated with the receive antenna, and a base spatial cross correlation matrix at the transmitter (RT _X , and at the receiver (RR _X ), respectively, are given by R _TX = = R _{D2D M} = , the method

comprising:

• for each path (n = 1 ... N)

Θ

· generating an angle of departure (AoD) ( "- ^AoD ) of the path from the transmit antenna to

Θ

the cluster of transmit scatterers, and generating an angle of arrival (AO A) ( "· ^ΑοΛ ) of the path at the receive antenna from the cluster of receive scatterers;

generating an angle of departure offset (Δι _Αο ο) for each of the (L) individual transmit scatterers within the cluster of transmit scatterers, and generating an angle of arrival offset (A _{M AoA} ) for each of the individual receive scatterers within the cluster of receive scatterers; and

Q

using the AoD ( "- ^AoD ) and the (L) angle of departure offsets (Δ^ο) to calculate (L)

Q

individual AoDs ( ⁿ ^ ^AoD ) of the path from the transmit antenna to the respective

Θ

individual transmit scatterers, and using the AoA ( ⁿ ' ^AoA ) and the angle of arrival offsets

Q

(Δ _ΠΙ ,Α _Ο Α) to calculate individual AoAs ( ⁿ - ^m > ^AoA ) of the path at the receive antenna from the respective individual receive scatterers;

θ Θ

• using the (L) individual AoDs ( ^nJ>AoD ) and Ao As ( " ^•m - ^AaA Calculated for each of the (N) paths to calculate JV x L AoA/ AoD values ( 0 _{nJ AoD/AoA} ),

• generating the entries ( ) in the base spatial cross correlation matrices, and

· generating the common spatial channel correlation matrix (RD2D, spatial) from the Kronecker product of the base spatial cross correlation matrices (i.e. Ro2D,spatiai ⁼ Rrx®Rj _? *)- (27) The method as claimed in Item 26 wherein the entries (p) in the base spatial cross

correlation matrices are generated using the formula:

where Ad is a normalised distance between two transmitter or receiver antenna elements, k is a wave number given by k = ^ and λ is the transmission wavelength.

A.

(28) The method as claimed in Item 26 comprising assigning medium correlation values in the range 0.1 to 0.4 for the entries (p) in the base spatial cross correlation matrices such that the generated common spatial channel correlation matrix {R DID, spatial) is for medium correlation.

(29) The method as claimed in Item 28 wherein the assigned medium correlation value for the entries (p) in the base spatial cross correlation matrices is 0.25.

(30) The method as claimed in Item 26 comprising assigning high correlation values in the range 0.7 to approximately 0.9 for the entries (p) in the base spatial cross correlation matrices such that the generated common spatial channel correlation matrix (RD2D,spatiai) is for high correlation.

(31) The method as claimed in Item 30 wherein the assigned high correlation value for the entries (p) in the base spatial cross correlation matrices is 0.8.

[0070]

The methods in any one of Item 25 to 31 may be suitable for computer implementation, and may therefore be implemented using a computer. For example, for both forms of the invention, a computer implemented simulator might be provided which is operable to perform the method.

[0071]

(32) A model for use in simulations relating to a wireless transmission path (n) from a

moving transmit antenna (s) to a moving receive antenna (u), wherein the transmission path includes a cluster of transmit scatterers associated with the transmit antenna and a cluster of receive scatterers associated with the receive antenna, the model comprising:

Q

© an angle of departure ( "- ^AoD ) of the path from the transmit antenna to the cluster of transmit

g

scatterers, and an angle of arrival ( " · ^ΑοΛ ) of the path at the receive antenna from the cluster of receive scatterers;

• an angle of departure offset (Δ _{Ζ AoD} ) for one or more individual transmit scatterers within the cluster of transmit scatterers, and an angle of arrival offset (Δ^ _Ο Λ) for ^on e or more individual receive scatterers within the cluster of receive scatterers;

g

• one or more individual angles of departure ( "J- ^AoD ) of the path from the transmit antenna to the one or more respective individual transmit scatterers, wherein the one or more individual

θ Θ

angles of departure ( ⁿ - ^l ' ^AoD ) are calculated using the angle of departure ( "· ^Αο ° ) and the one or more angle of departure offsets (A _{i j4oD} );

β

• one or more individual angles of arrival ( ⁿ - ^m - ^AoA ) of the path at the receive antenna from the respective one or more individual receive scatterers, wherein the one or more individual θ Θ

angles of arrival ( ⁿ > ^m - ^AoA ) are calculated using the angle of arrival ( ⁿ ' ^AoA ) and the one or more angle of arrival offsets (& _{m AoA} ); and

a channel coefficient (h _{n u s} (t) ) which can be calculated using the one or more individual angles θ Θ

of departure ( "' ^l ' ^AoD ) and the one or more individual angles of arrival ( "- ^m · ^ΑοΑ ).

(33) The model as claimed in Item 32 wherein the cluster of transmit scatterers associated with the transmit antenna is located in a transmit-scatterer-ring surrounding (or otherwise associated with) the moving transmit antenna, and the cluster of transmit scatterers is interpreted as a "virtual-transmitter" so that the aggregation of power received at all scatterers in the cluster of transmit scatterers reaches the cluster of receive scatterers associated with the receive antenna as a single wave.

[0072]

The above-mentioned processing may be executed by a computer (a user equipment, a simulator, etc.). Also, it is possible to provide a computer program which causes a programmable computer device to execute the above - mentioned processing. The program can be stored and provided to a computer using any type of non-transitory computer readable media.

Non-transitory computer readable media include any type of tangible storage media. Examples of non-transitory computer readable media include magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), optical magnetic storage media (e.g. magneto-optical disks), CD-ROM, CD-R, CD-R/W, and semiconductor memories (such as mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access

Memory), etc.). The software modules may be provided to a computer using any type of transitory computer readable media. Examples of transitory computer readable media include electric signals, optical signals, and electromagnetic waves. Transitory computer readable media can provide the software modules to a computer via a wired communication line (e.g. electric wires, and optical fibers) or a wireless communication line.

[0073]

This application is based upon and claims the benefit of priority from Australian provisional patent application No.2013901565, filed on May 3, 2013, the disclosure of which is incorporated herein in its entirely by reference.

Reference Signs List [0074]

100 MODEL

lOl .a TRANSMITTER

lOl .b RECEIVER

102.a Tx-SCATTERING-RING

102.b Rx-SCATTERING-RING

103 I ^th PATH

104 TRANSMIT SCATTERER TS,

105 m' ^h PATH

106 SCATTERER RS _m

200 MODEL

201. a TRANSMITTER

201.b RECEIVER

202.a Tx-SCATTERING-RING

202.b Rx-SCATTERING-RING

203 I ^th PATH

204 TRANSMIT SCATTERER TS,

205.a SPACING S _T

205.b SPACING S _R

206 SCATTERER RS _m

300 MODEL

301.a TRANSMITTER

301.b RECEIVER

302.a Tx-SCATTERING-RING

302.b Rx-SCATTERING-RING

303.a TRANSMIT-SCATTERER-CLUSTER

303.1.a Tx-SCATTERER TS,

303.b RECEIVE-SCATTERER-CLUSTER

303.m.b m' ^h Rx-SCATTERER RS _m

304 SINGLE PATH

305.a SPACING δ _τ SPACING 5 _R

DISTRIBUTION OF AoDs

DISTRIBUTION OF AoAs

MODEL

TRANSMITTER

RECEIVER

Tx-SCATTERING-RING

Rx-SCATTERING-RING

CLUSTER OF Tx-SCATTERERs

CLUSTER OF Rx-SCATTERERs

SINGLE WAVE