BACKGROUND OF THE INVENTION

Field of the Invention

The present document is directed to a random access scheme to the network. More specifically, the present document is directed to an enhanced cyclic shift used for static device, such as M2M (Machine to Machine) communication device, to use at performing random access to the network. Discussion of the Related Art

First of all, 3GPP LTE (3 ^rd generation partnership project) long term evolution: hereinafter called 'LTE') communication system is schematically described as a mobile communication system to which the present invention is applicable.

FIG. 1 is a schematic diagram of E-UMTS network structure as an example of a mobile communication system.

Referring to FIG. 1, E-UMTS (evolved universal mobile telecommunications system) is the system having evolved from UMTS (universal mobile telecommunications system) and its basic standardization is ongoing by 3 GPP. Generally, the E-UMTS can be called LTE system.

E-UMTS network can be mainly divided into E-UTRAN (evolved-UMTS terrestrial radio access network) 101 and CN 102 (core network). The E-UTRAN 101 consists of a user equipment (hereinafter abbreviated UE) 103, a base station (hereinafter named eNode B or eNB) 104, and an access gateway (hereinafter abbreviated AG) 105 located at an end point of the network to be externally connected to an external network. The AG 105 can be divided into one part responsible for user traffic processing and the other part for processing control traffic. In this case, the AG for new user traffic processing and the AG for processing control traffic can communicate with each other using a new interface.

At least one cell can exist at one eNode B. Between eNode Bs, an interface for user or control traffic transmission is usable. And, the CN 102 can consist of a node for user registrations of the AG 105 and other UE 103. Moreover, an interface for discriminating the E-UTRAN 101 and the CN 102 is available.

Layers of a radio interface protocol between a user equipment and a network can be divided into LI (first layer), L2 (second layer) and L3 (third layer) based on three lower layers of the open system interconnection (OSI) reference model widely known in the field of communication systems. A physical layer belonging to the first layer provides an information transfer service using a physical channel. A radio resource control (hereinafter abbreviated RRC) located on the third layer plays a role in controlling radio resources between the user equipment and the network. For this, the RRC layers exchange RRC messages between the user equipment and the network. The RRC layers can be distributed to network nodes including the eNode B 104, the AG 105 and the like. Moreover, the RRC layer can be provided to the eNode B 104 or the AG 105 only.

FIG. 2 and FIG. 3 are diagrams for structures of a radio interface protocol between a user equipment and UTRAN based on the 3GPP radio access network specifications.

Referring to FIG. 2 and FIG. 3, a radio interface protocol horizontally consists of a physical layer, a data link layer and a network layer. And, the radio interface protocol vertically consists of a user plane for data information transfer and a control plane for control signal delivery (signaling). In particular, FIG. 2 shows the respective layers of the radio protocol control plane and FIG. 3 shows the respective layers of the radio protocol user plane. The radio protocol layers shown in FIG. 2 and FIG. 3 can be divided into LI (first layer), L2 (second layer) and L3 (third layer) based on three lower layers of the open system interconnection (OSI) reference model widely known in the field of communication systems. The respective layers of the radio protocol control plane shown in FIG. 2 and the respective layers of the radio protocol user plane shown in FIG. 3 are explained as follows.

First of all, a physical (PHY) layer of a first layer provides an upper layer with an information transfer service using a physical channel. The physical (PHY) layer is connected to a medium access control (MAC) layer on an upper layer via a transport channel. And, data is transported between the medium access control (MAC) layer and the physical (PHY) layer via the transport channel. In this case, the transport channel can be classified into a dedicated transport channel or a common transport channel according to whether a channel is shared or not. Moreover, data are transported via the physical channel between different physical layers, i.e., between a physical layer of a transmitting side and a physical layer of a receiving side.

Various layers exist in the second layer. First of all, a medium access control (hereinafter abbreviated 'MAC') layer plays a role in mapping various logical channels to various transport channels. And, the MAC layer also plays a role as logical channel multiplexing in mapping several logical channels to one transport channel. The MAC layer is connected to a radio link control (RLC) layer of an upper layer via a logical channel. And, the logical channel can be mainly categorized into a control channel for transferring information of a control plane and a traffic channel for transferring information of a user plane according to a type of the transferred information.

A radio link control (hereinafter abbreviated RLC) of the second layer performs segmentation and concatenation on data received from an upper layer to play a role in adjusting a size of the data to be suitable for a lower layer to transfer the data to a radio section. And, the RLC layer provides three kinds of RLC modes including a transparent mode (hereinafter abbreviated TM), an unacknowledged mode (hereinafter abbreviated UM) and an acknowledged mode (hereinafter abbreviated AM) to secure various kinds of QoS demanded by each radio bearer (hereinafter abbreviated RB). In particular, the AM RLC performs a retransmission function through automatic repeat and request (ARQ) for the reliable data transfer.

A packet data convergence protocol (hereinafter abbreviated PDCP) layer of the second layer performs a header compression function for reducing a size of an IP packet header containing relatively large and unnecessary control information to efficiently transmit such an IP packet as IPv4 and IPv6 in a radio section having a small bandwidth. This enables a header part of data to carry mandatory information only to play a role in increasing transmission efficiency of the radio section. Moreover, in the LTE system, the PDCP layer performs a security function as well. This consists of ciphering for preventing data interception conducted by a third party and integrity protection for preventing data manipulation conducted by a third party.

A radio resource control (hereinafter abbreviated RRC) layer located at a most upper part of a third layer is defined in the control plane only and is responsible for controlling a logical channel, a transport channel and physical channels in association with configuration, reconfiguration and release of radio bearers (hereinafter abbreviated RBs). In this case, the RB means a logical path provided by the first and second layers of the radio protocol for the data delivery between the user equipment and the UTRAN. Generally, configuring an RB means to stipulate characteristics of radio protocol layers and channels required for providing a specific service and also means to configure detailed parameters and operational methods thereof. The RB can be classified into a signaling RB (SRB) or a data RB DRB). The SRB is used as a path for sending an RRC message in a control plane (C-plane) and the DRB is used as a path for transferring user data in a user plane (U-plane). As a downlink transport channel for transporting data to a user equipment from a network, there is a broadcast channel (BCH) for transmitting system information and a downlink shared channel (SCH) for transmitting a user traffic or a control message. Downlink multicast, traffic of a broadcast service or a control message can be transmitted on downlink SCH or a separate downlink MCH (multicast channel). Meanwhile, as an uplink transport channel for transmitting data to a network from a user equipment, there is a random access channel (RACH) for transmitting an initial control message or an uplink shared channel (SCH) for transmitting user traffic or a control message.

As a downlink physical channel for transmitting information transferred on a downlink transport channel to a radio section between a network and a user equipment, there is a physical broadcast channel for transferring information of BCH, a physical multicast channel (PMCH) for transmitting information of MCH, a physical downlink shared channel for transmitting information of PCH and downlink SCH or a physical downlink control (or called DL L1/L2 control channel) for transmitting control information provided by first and second layers.

As an uplink physical channel for transmitting information forwarded on an uplink transport channel to a radio section between a network and a user equipment, there is a physical uplink shared channel (PUSCH) for transmitting information of uplink SCH, a physical random access channel (PRACH) for transmitting RACH information or a physical uplink control channel (PUCCH) for transmitting such control information, which is provided by first and second layers, as HARQ AC , HARQ NACK, scheduling request (SR), channel quality indicator (CQI) report and the like.

An LTE User Equipment (UE) can only be scheduled for uplink transmission if its uplink transmission timing is synchronized. The LTE Random Access CHannel (RACH) therefore plays a key role as an interface between non-synchronized UEs and the orthogonal transmission scheme of the LTE uplink radio access.

According to the current LTE system, there are 64 preambles to be used by the UE at performing random access to the network. These sequences can be distinguished by a root index and a cyclic shift applied thereto.

Normally, network determines whether the UEs within its cell are high speed devices. And, the network may signals the UEs to use a cyclic shift in restricted mode when it determines that the UEs in its cell are high speed devices. However, there can be a static device, in its nature, such as M2M device, within the cell where the network determines as high speed cell. When we consider the nature of the static device, we can provide enhanced cyclic shift for the random access.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an enhanced cyclic shift used for static device, such as M2M (Machine to Machine) communication device, to use at performing random access to the network.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method for a device to perform a random access to the network, the method comprising: receiving system information from the network, wherein the system information comprises a high speed flag, wherein the high speed flag with a first value indicates a first mode and the high speed flag with a second value indicates a second mode; and transmitting a random access preamble sequence generated from a Zaddoff Chu (ZC) sequence with a cyclic shift value, wherein the cyclic shift value is differently determined according to the first mode and the second mode, and wherein the device with a static characteristic determines the cyclic shift value according to the first mode, even when the high speed flag indicates the second mode is proposed.

Here, the system information may further comprise zero correlation zone configuration information indicating Ncs value, and wherein the cyclic shift value is determined as integer multiple of the Ncs value according to the first mode.

The zero correlation zone configuration information may indicate different values of the Ncs value for the first mode and the second mode.

Preferably, the device with the static characteristic may determine the value of the Ncs value according to the first mode, even when the high speed flag indicates the second mode.

On the other hand, the cyclic shift value can be determined considering a cyclic shift corresponding to a Doppler shift of magnitude 1/T _S E _Q , when the cyclic shift value is to be determined according to the second mode, where the T _S E _Q represents a time domain length of a sequence part of the random access preamble sequence.

The device with the static characteristic may comprise a M2M (Machine to Machine) communication device.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method for a network to control a random access from a device, the method comprising: transmitting system 0 information to the device, wherein the system information comprises a high speed flag, wherein the high speed flag with a first value indicates a first mode and the high speed flag with a second value indicates a second mode; and detecting a random access preamble sequence generated from a Zaddoff Chu (ZC) sequence with a cyclic shift value, wherein the cyclic shift value is differently determined according to the first mode and the second mode, and wherein the network tries to detect the random access preamble sequence for both of the cases when the device transmitted the random access preamble with the cyclic shift value according to the first mode and when the device transmitted the random access preamble with the cyclic shift value according to the second mode, even when the network transmitted the system information with the high speed flag indicating the second mode is proposed.

The device may comprise a device with a static characteristic. And, the device with the static characteristic may comprise a M2M (Machine to Machine) communication device.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a device with a static characteristic and performing a random access to the network, the device comprising: a receiver configured to receive system information from the network, wherein the system information comprises a high speed flag, wherein the high speed flag with a first value indicates a first mode and the high speed flag with a second value indicates a second mode; a transmitter configured to transmit a random access preamble sequence generated from a Zaddoff Chu (ZC) sequence with a cyclic shift value, wherein the cyclic shift value is differently determined according to the first mode and the second mode; and a processor connected to the receiver and the transmitter, configured to determines the cyclic shift value according to the first mode, even when the high speed flag indicates the second mode is proposed.

The system information may further comprise zero correlation zone configuration information indicating Ncs value, and the processor may be configured to determine the cyclic shift value as integer multiple of the Ncs value according to the first mode. The zero correlation zone configuration information may indicate different values of the Ncs value for the first mode and the second mode.

The processor may determine the value of the Ncs value according to the first mode, even when the high speed flag indicates the second mode.

On the other hand, the processor may determine the cyclic shift value considering a cyclic shift corresponding to a Doppler shift of magnitude 1/T _SEQ , when the cyclic shift value is to be determined according to the second mode, and where the T _SEQ represents a time domain length of a sequence part of the random access preamble sequence.

The device may comprise a M2M (Machine to Machine) communication device.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a network for controlling a random access from a device, the network comprising: a transmitter configured to transmit system information to the device, wherein the system information comprises a high speed flag, wherein the high speed flag with a first value indicates a first mode and the high speed flag with a second value indicates a second mode; and a receiver configured to detect a random access preamble sequence generated from a Zaddoff Chu (ZC) sequence with a cyclic shift value, wherein the cyclic shift value is differently determined according to the first mode and the second mode, and a processor connected to the transmitter and the receiver, and configured to control the receiver to try to detect the random access preamble sequence for both of the cases when the device transmitted the random access preamble with the cyclic shift value according to the first mode and when the device transmitted the random access preamble with the cyclic shift value according to the second mode, even when the network transmitted the system information with the high speed flag indicating the second mode is proposed.

The device may comprise a device with a static characteristic, and the device with the static characteristic may comprise a M2M (Machine to Machine) communication device.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:

Figure 1 is a schematic diagram of E-UMTS network structure as an example of a mobile communication system;

Figures 2 and 3 are diagrams for structures of a radio interface protocol between a user equipment and UTRAN based on the 3GPP radio access network specifications;

Figure 4 shows the contention-based procedure consists of four-steps;

Figure 5 shows the non-contention-based procedure consists of two-steps;

Figure 6 shows the required dimension of the cyclic shift unit; Figure 7 shows the effect of frequency offset;

Figure 8 provides the key elements of M2M Domain; and

Figure 9 shows apparatus for implementing the present invention. DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In the following detailed description of the invention includes details to help the full understanding of the present invention. Yet, it is apparent to those skilled in the art that the present invention can be implemented without these details. For instance, although the following detailed description is made in detail on the assumption that a mobile communication system is the 3 GPP LTE system, it is applicable to other prescribed mobile communication systems by excluding unique items of the 3 GPP LTE.

Occasionally, the structures and devices known to the public are omitted to avoid conceptional vagueness of the present invention or can be illustrated as block diagrams centering on their core functions.

Besides, in the following description, assume that a terminal is a generic term of such a mobile or fixed user-end device as a user equipment (UE), a mobile station (MS) and the like. Moreover, assume that eNB is a generic name of such a random node of a network end, such as a base station, which communicates with a terminal, as a Node B, an eNnode B and the like.

As stated above, the present invention is directed to an enhanced cyclic shift used for static device, such as M2M (Machine to Machine) communication device, to use at performing random access to the network. For better understanding of the invention, a random access procedure of the LTE system is first explained as an example.

The LTE random access procedure comes in two forms, allowing access to be either contention-based (implying an inherent risk of collision) or contention-free. A UE initiates a contention-based random access procedure for all use-cases listed as following.

(1) A UE in RRC CONNECTED state, but not uplink-synchronized, needing to send new uplink data or control information (e.g. an event-triggered measurement report);

(2) A UE in RRC CONNECTED state, but not uplink-synchronized, needing to receive new downlink data, and therefore to transmit correspondingACK/NACK in the uplink;

(3) A UE in RRC CONNECTED state, handing over from its current serving cell to a target cell;

(4) A transition from RRC IDLE state to RRC CONNECTED, for example for initial access or tracking area updates;

(5) Recovering from radio link failure.

In this procedure, a random access preamble signature is randomly chosen by the UE, with the result that it is possible for more than one UE simultaneously to transmit the same signature, leading to a need for a subsequent contention resolution process.

For the use-cases (2) (new downlink data) and (3) (handover) the eNodeB has the option of preventing contention occurring by allocating a dedicated signature to a UE, resulting in contention-free access. This is faster than contention-based access - a factor which is particularly important for the case of handover, which is time-critical.

Unlike in WCDMA, a fixed number (64) of preamble signatures is available in each LTE cell, and the operation of the two types of RACH procedure depends on a partitioning of these signatures between those for contention-based access and those reserved for allocation to specific UEs on a contention-free basis.

The two procedures are outlined in the following. KR2012/001580

FIGs. 4 and 5 are procedural diagrams illustrating Contention-based Random Access

Procedure and Non-Contention-based Random Access Procedure.

The contention-based procedure consists of four-steps as shown in Figure 4:

• Step 1 : Preamble transmission (message 1);

· Step 2: Random access response (message 2);

• Step 3: Layer 2 / Layer 3 (L2/L3) message (message 3);

• Step 4: Contention resolution message (message 4).

The slightly unpredictable latency of the random access procedure can be circumvented for some use cases where low latency is required, such as handover and resumption of downlink traffic for a UE, by allocating a dedicated signature to the UE on a per-need basis. In this case the procedure is simplified as shown in Figure 5. The procedure terminates with the RAR.

As noted above, 64 PRACH signatures are available in LTE, compared to only 16 in WCDMA. This can not only reduce the collision probability, but also allow for 1 bit of information to be carried by the preamble and some signatures to be reserved for contention free access. Therefore, the LTE PRACH preamble called for an improved sequence design with respect to WCDMA. While Pseudo-Noise (PN) based sequences were used in WCDMA, in LTE prime-length Zadoff-Chu (ZC) sequences have been chosen. These sequences enable improved PRACH preamble detection performance.

th

When the root index of the Zadoff-Chu sequence is represented as 'u\ the W root Zadoff-Chu sequence is defined by:

[E uation 1] where ^ ZC represents the length of the Zadoff-Chu sequence.

From the U root Zadoff-Chu sequence, random access preambles with zero correlation zones of length ^cs ^— ^ are defined by cyclic shifts according to:

[Equation 2]

(«) = *„((» + C _v ) mod N _zc ) where Cv represents a cyclic shift value and is multiple of Ncs in normal mode. And, N _C s can be referred to as basic cyclic shift unit.

Sequences obtained from cyclic shifts of different ZC sequences are not orthogonal. Therefore, orthogonal sequences obtained by cyclically shifting a single root sequence should be favored over non-orthogonal sequences; additional ZC root sequences should be used only when the required number of sequences (64) cannot be generated by cyclic shifts of a single root sequence. The cyclic shift dimensioning is therefore very important in the RACH design.

Figure 6 shows the required dimension of the cyclic shift unit.

The cyclic shift offset Ncs is dimensioned so that the Zero Correlation Zone (ZCZ) of the sequences guarantees the orthogonality of the PRACH sequences regardless of the delay spread and time uncertainty of the UEs. The minimum value of Ncs should therefore be the smallest integer number of sequence sample periods that is greater than the maximum delay spread and time uncertainty of an uplink non-synchronized UE, plus some additional guard samples provisioned for the spill-over of the pulse shaping filter envelope present in the PRACH receiver (see. Figure 6).

However, the support of 64 RACH preambles as described above assumes little or no frequency shifting due to Doppler spread, in the presence of which ZC sequences lose their zero autocorrelation property. In the presence of a frequency offset Sf, it can be shown that the PRACH ZC sequence is distorted to have, at least, two unwanted side peaks (or aliasing).

Figure 7 shows the effect of frequency offset.

In Figure 7, C.| and C ₊ ] indicate the unwanted side peaks with the presence of a frequency offset. Due to this restriction, cyclic shifts should be limited to a certain level.

Therefore, design of the cyclic shift for RACH shall be divided into the above two cases, (1 ) unrestricted mode and (2) restricted mode (due to high frequency offset).

Network normally determines whether the UEs within its cell are high speed devices. For example, when the cell is located near the high speed train, the network for that cell may decide to use cyclic shift for restricted mode. Network normally signals whether the UE has to use cyclic shifts for unrestricted mode or restricted mode via HighSpeedFlag. According to the current LTE standard, UE has to follow the mode selected by the network.

However, there can be a static device having very low mobility in its nature, such as M2M device, within the cell where the network determines as high speed cell. When we consider the nature of the static device, we can provide enhanced cyclic shift for the random access. As one of stereotypes of static device, the M2M device is considered. Machine to Machine (M2M) Communication is seen as a form of data communication between entities that do not necessarily need human interaction. It is different to current communication models as it involves: new or different market scenarios. M2M bears enormous application diversity, below is some application domain example :

Security:

Alarm systems, backup for landline, access control, car/driver security, etc.. . Metering:

Power, gas, water, heating, grid control, etc...

Health:

Monitoring vital signs, supporting the aged or handicapped, web access telemedicine points, remote diagnostics, etc...

Tracking & Tracing:

Fleet management, order management, pay as you drive, asset tracking, navigation, traffic information, etc...

Payment:

· Vending machines, gaming machines, point of sales, etc...

Etc...

Figure 8 provides the key elements of M2M Domain:

Referring to Figure 8, the M2M Device Domain is a M2M area that provide connectivity between M2M Devices and M2M Gateways, e.g. Personal Area Network technologies such as IEEE 802.15, SRD, UWB, Zigbee, Bluetooth, etc, or local networks such as PLC, M- BUS, Wireless M-BUS.

M2M Device is a device capable of replying to requests (or transmitting) for data contained within those devices autonomously. Such devices run M2M applications using M2M Service Capabilities. They can be connected to the Network domain either directly via the access network(s) or via M2M gateway(s) as e network proxy.

M2M Gateways use M2M capabilities to ensure M2M Devices inter working and interconnection to the communications network (Network Domain).

In figure 8, the M2M Core Network Domain provides connectivity between the M2M Device(s)/Gateway(s) and M2M application (server). It can be further split into Access transport and Core networks, e.g.: xDSL, PLC, satellite, LTE, GERAN, UTRAN, eUTRAN, W-LAN, WiMAX, etc.

M2M Application Domain (Server) contains the middleware layer where data goes through various application services and is used by the specific business-processing a software agent, or process by which the data can be analyzed, reported, and acted upon.

As can be seen above, M2M device, in its nature, has static characteristics. For example, the M2M device (e.g. power metering device) can be located in a cell identified by the network as having the UEs with high mobility. In this case, if this static device should follow the signaling of the network indicating the restricted mode, we might waist the available signatures for PRACH.

One aspect of the present proposal is for a method for a device to perform a random access to the network. This method comprises: receiving system information from the network, wherein the system information comprises a high speed flag, wherein the high speed flag with a first value indicates a first mode and the high speed flag with a second value indicates a second mode; and transmitting a random access preamble sequence generated from a Zaddoff Chu (ZC) sequence with a cyclic shift value, wherein the cyclic shift value is differently determined according to the first mode and the second mode, and wherein the device with a static characteristic determines the cyclic shift value according to the first mode, even when the high speed flag indicates the second mode. This aspect of the invention is more specifically explained.

The system information received from the network may comprise PRACH-Config.

The IE PRACH-ConfigSIB and IE PRACH-Config are used to specify the PRACH configuration in the system information and in the mobility control information, respectively. able 1

PRACH-Config information elements

-- ASN1 START

P ACH-ConfigSIB ::= ! SEQUENCE {

rootSequencelndex INTEGER (0..837),

prach-Configlnfo PRACH-Configlnfo

}

PRACH-Config ::= SEQUENCE {

rootSequencelndex INTEGER (0..837),

prach-Configlnfo PRACH-Configlnfo OPTIONAL

}

PRACH-Configlnfo ::= SEQUENCE {

prach-Configlndex INTEGER (0..63),

highSpeedFlag BOOLEAN,

zeroCorrelationZoneConfig INTEGER (0..15),

prach-FreqOffset INTEGER (0..94)

}

- ASN1 STOP In the table 1 , rootSequencelndex indicates the root index u of the ZC sequence, and by using this information u ^th root ZC sequence is defined by Equation 1, where the length N zc of the Zadoff-Chu sequence is given by Table 2.

[Table 2]

In table 1 , prach-Configlndex indicates preamble format, system frame number, and subframe number for PRACH. See table 3.

[Table 3]

In table 1, highSpeedFlag indicates whether the UE is to select cyclic shift according to a first mode (unrestricted mode) or a second mode (restricted mode). HighSpeedFlag with TRUE value may indicate the unrestricted mode and HighSpeedFlag with FALSE value may indicate the restricted mode.

In table 1 , zeroCorrelationZoneConfig is to indicate parameter Ncs, but Ncs value is differently acquired by the following table 4. Table 4 is for Ncs preamble generation (preamble formats 0-3).

[Table 4] 1 13 18

2 15 22

3 18 26

4 22 32

5 26 38

6 32 46

7 38 55

8 46 68

9 59 82

10 76 100

1 1 93 128

12 119 158

13 167 202

14 279 237

15 419 -

Based on this information, the device according to the present proposal can transmit random access preamble sequence generated from u ^th ZC sequence to the network. It should be noted that the cyclic shift value is differently determined according to the restricted mode and unrestricted mode.

Specifically, from the « ^th root Zadoff-Chu sequence, random access preambles with zero correlation zones of length N _cs -l are defined by cyclic shifts according to the Equation 2 where the cyclic shift is given by following equation. Equation 3]

^CS is given by Table 4 for preamble formats 0-3. The parameter High-speed-flag provided by higher layers determines if unrestricted set or restricted set shall be used. However, the device with a static characteristic, such as M2M device, may determine the N _cs parameter and C _v value for the unrestricted set even though the network signaled Highspeed-flag with FALSE value. By using this scheme, the system can more efficiently use the available cyclic shifts.

The variable ^a u of [equation 3] is the cyclic shift corresponding to a Doppler shift of magnitude (TSEQ represents the time domain length of the sequence part of the random access preamble; it corresponds to the cyclic shift corresponding to one subcarrier spacing) and is given by

[Equation 4]

where P is the smallest non-negative integer that fulfils ( ?w)mod V _zc = 1 . The parameters for restricted sets of cyclic shifts depend on . For ^CS— ^< ^ZC , the parameters are given by

[Equation 5] "shift

RA

d start 2d U ¾ift N ^V , CS

RA

n group ^ZcMtartJ

"shift maxfli (iY _zc - 2rf _M ft

o

For N _zc /3≤d _u ≤(N _zc ~N _cs )/2 _he parameters are given by

[Equation 6]

_M RA

shift L(V _zc -2^)/V _cs J start _zc -2^+^ _ft 7Y _cs

ft

"group d ¹ -* start CS J o RA

shift

For all other values of ^u u , there are no cyclic shifts in the restricted set.

We had exemplified the device with the static characteristic as M2M device. However, the device with the statistic characteristic may include other type of device.

Network according to the present proposal may operate as following.

According to the present proposal, even though the network signaled the HighSpeedFlag indicating the second mode (restricted mode), some device with statistic characteristic may P T/KR2012/001580 use cyclic shift set for unrestricted mode. Therefore, the network according to the present proposal may detect the RACH preamble sequence both with the cyclic shift for unrestricted mode and the cyclic shift for restricted mode, even though the network informed the restricted mode. It is based on the assumption that the network knows there can be a device with static characteristic.

In order to detect the preamble with the cyclic shift according to both of the unrestricted mode and restricted mode, the network may try to detect the preamble with both types of cyclic shift even though it signaled UEs of restricted mode. It is possible that the static device, such as M2M device, registered with the network as static device before it starts random access to the network. Alternatively, the network may, by default, try to detect the preamble with both types of cyclic ^" shift even though it signaled the HighSpeedFlag as FALSE (meaning restricted mode).

Hereinafter, the apparatus for implementing the above proposal is explained.

Figure 9 shows apparatus for implementing the present invention.

In figure 9, a wireless communication system includes a BS 10 and one or more UE 20. In downlink, a transmitter may be a part of the BS 10, and a receiver may be a part of the UE

20. In uplink, a transmitter may be a part of the UE 20, and a receiver may be a part of the BS 10. A BS 10 may include a processor 1 1 , a memory 12, and a radio frequency (RF) unit 13. The processor 1 1 may be configured to implement proposed procedures and/or methods described in this document. The memory 12 is coupled with the processor 1 1 and stores a variety of information to operate the processor 1 1. The RF unit 13 is coupled with the processor 1 1 and transmits and/or receives a radio signal. A UE 20 may include a processor

21 , a memory 22, and a RF unit 23. The processor 21 may be configured to implement proposed procedures and/or methods described in this application. The memory 22 is coupled with the processor 21 and stores a variety of information to operate the processor KR2012/001580

21. The RF unit 23 is coupled with the processor 21 and transmits and/or receives a radio signal. The BS 10 and/or the UE 20 may have single antenna and multiple antenna. When at least one of the BS 10 and the UE 20 has multiple antenna, the wireless communication system may be called as multiple input multiple output (MIMO) system.

In figure 9, the UE may comprise static device, such as M2M device. In this case, the processor 21 can be configured to use cyclic shift according to unrestricted mode even when the RF Unit 23 receives system information indicating the restricted mode.

The above-described enhanced random access technology and apparatus are explained mainly with reference to the example that they are applied to the 3 GPP LTE system. However, they are applicable to various mobile communication systems, such as IEEE based system employing ranging procedure corresponding to the random access procedure of LTE.