A mobile node in a wireless communication system

TECHNICAL FIELD

The present disclosure relates to a wireless communication system comprising at least one mobile node arrangement and a plurality of fixed arranged along a track and adapted to cover a corresponding zone.

BACKGROUND

Internet access on high speed trains such as Hyperloop, Maglev, and conventional railway systems is of utmost importance since the ability to work, watch movies and play games is expected by most travelers nowadays. Unfortunately, providing data to such trains is a big backhaul challenge. Each train with for example 500 people consuming 2 Mbit/s requires continuous 1 Gbit/s data or more into the train, which is moving fast, often through rural areas with no or limited coverage by conventional mobile broadband systems such as long term evolution (LTE) or wideband code division multiple access (WCDMA).

Many train companies and suppliers try to provide dedicated Internet access on the train by means of local WiFi networks that are backhauled though multiple access methods including LTE, WCDMA as well as satellite based system. For ultra-high- speed rail systems that also are likely to remain in an enclosed environment such as a tunnel, the conventional access systems will not provide any useful service at all. Instead, the access system providing data to the users must be onboard the train so that the access points are moving together with the users. The main bottleneck is the backhaul system used to connect the train to a mobile core network or other supply networks.

Mobile access network are usually not designed to supply many hundreds of high capacity users on a train moving very fast through the landscape. Thus, even if special mobile networks were to be built along the railway tracks, the performance would barely meet the expectations from demanding customers on the trains. Technical problems associated with such deployment includes frequent roaming of hundreds of users, Doppler shift of LTE subcarriers that reduces performance for users on high-speed trains.

Existing systems are based on some kind of point-to-multi-point transmission in order to share capacity between different movable stations, and these systems inherently add large latency which doesn’t allow relaying data between multiple stations. For the proposed hyperloop trains, conventional access systems will not provide any useful service due to the very high-speed movement of the users. It is therefore a desire to provide a wireless communication system where a mobile node is served in a sufficient manner regarding Internet access.

SUMMARY

It is an object of the present disclosure to provide a wireless communication system where power is saved, link budget improved and the time needed for a user terminal to connect to the base station is decreased.

Said object is obtained by means of a wireless communication system comprising at least one mobile node arrangement and a plurality of fixed nodes arranged along a track and adapted to cover a corresponding zone, along which track at least one corresponding mobile node arrangement is adapted to travel. Each fixed node is adapted to communicate with its adjacent fixed node or nodes, where at least one fixed node constitutes a gateway node that is connected to a core network and the other fixed nodes constitute intermediate nodes. Each mobile node arrangement is adapted to replace at least one fixed node while at least partly being present in the corresponding zone.

Said object is also obtained by means of a method for maintaining communication between at least one mobile node arrangement and a core network using a plurality of fixed nodes arranged along a track and used to cover a corresponding zone, along which track at least one mobile node arrangement is adapted to travel. Each fixed node is used for communicating with its adjacent fixed node or nodes, where at least one fixed node constitutes a gateway node that is connected to a core network and the other fixed nodes constitute intermediate nodes. The method comprises replacing at least one fixed node with at least one mobile node arrangement while said mobile node arrangement at least partly is present in the corresponding zone. This provides an advantage of providing a sufficient coverage for a mobile node such as for example a high-speed train or some other mass transportation vehicle, where the only modification required is the ability to quickly turn the transmitter on and off according to some performance measure or signaling. A further advantage is the possibility to create cost efficient communication system since network access is only required at very few positions along the track. A relatively low latency is acquired even with many relayed fixed nodes, and is thus perfectly suited to backhaul systems such as LTE or 5G. Said object is also obtained by means of a mobile node arrangement adapted to travel along a track and to communicate with adjacent fixed nodes among a plurality of fixed nodes arranged along a track and adapted to cover a corresponding zone. The mobile node arrangement is adapted to replace at least one fixed node while at least partly being present in the corresponding zone.

This provides an advantage of providing a sufficient coverage for a mobile node such as for example a high-speed train or some other mass transportation vehicle, where the only modification required is the ability to quickly turn the transmitter on and off according to some performance measure or signaling.

According to some aspects, when there are a first mobile node arrangement and second mobile node arrangement in a common zone that belongs to an intermediate node, each mobile node arrangement is adapted to communicate with a fixed node that is positioned closer to itself than the other mobile node arrangement.

This provides an advantage of handling two mobile node arrangements in the same zone. According to some aspects, each fixed node is adapted to communicate via a first communication resource and a second communication resource. This means that each fixed node having two adjacent fixed nodes is arranged to transmit signals to a first adjacent fixed node and to receive signals from a second adjacent fixed node via either the first communication resource or the second communication resource, and to transmit signals to the second adjacent fixed node and to receive signals from the first adjacent fixed node via the other of said communication resources.

This provides an advantage of reducing interference. The mobile node must be able to quickly swap communication resources, or this can be obtained by two radios turned on and off and traffic routed accordingly. No central roaming or scheduling management is required.

According to some aspects, each mobile node arrangement is arranged to communicate also via communication resources that differ from the first communication resource or the second communication resource.

According to some aspects, when at least one mobile node arrangement is present in a common zone that belongs to a gateway node, each mobile node arrangement that is closer to an adjacent fixed node than any other mobile node arrangement in said zone is adapted to communicate with said adjacent fixed node via communication resources that differ from the communication resources via which the gateway node is adapted to communicate with the adjacent fixed nodes. This provides an advantage of handling mobile node arrangements in a zone that belongs to a gateway node without interrupting any communication.

According to some aspects, when there are at least two mobile node arrangements in a common zone, these mobile node arrangements are adapted to communicate with each other via communication resources that differ from the communication resources used for communication with adjacent fixed nodes adapted to cover other zones. This provides an advantage of handling two or more mobile node arrangements in the same zone and at the same time admitting bi-directional communication.

According to some aspects, each gateway node is adapted to maintain communication with its adjacent nodes when one or more mobile node arrangements are present in the corresponding zone. This means that each one of said mobile node arrangements is adapted to terminate all communication while being present within the corresponding zone. This provides an advantage of handling mobile node arrangements in a zone that belongs to a gateway node in an uncomplicated manner.

According to some aspects, at least one gateway node comprises an electrically steerable antenna arrangement.

This provides an advantage of handling mobile node arrangements in a zone that belongs to a gateway node in an enhanced manner.

According to some aspects, at least one communication resources at least comprises a frequency channel.

According to some aspects, at least one communication resources at least comprises a time slot. According to some aspects, at least one communication resources at least comprises a coded channel.

According to some aspects, there are different communication resources between at least two adjacent pairs of fixed nodes.

This provides an advantage of enabling communication standards that use mixed communication resources. BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will now be described more in detail with reference to the appended drawings, where:

Figure 1 shows a schematical view of a first example where there is a mobile node in a zone in a wireless communication system; Figure 2 shows a schematical view of a second example where there are two mobile nodes in the same zone a wireless communication system;

Figure 3 shows a schematical view of a third example where there are three mobile nodes in the same zone a wireless communication system;

Figure 4 shows a schematical view of the second example where there are two mobile nodes in one zone and two other mobile nodes in another zone in a wireless communication system; Figure 5 shows a schematical view of a fourth example where there are two mobile nodes in the same zone a wireless communication system at a first instant;

Figure 6 shows a schematical view of the fourth example where there are two mobile nodes in the same zone a wireless communication system at a second instant;

Figure 7 shows a schematical view of a fifth example where there is a mobile node in a zone adjacent a zone of a gateway node, approaching the zone of the gateway node;

Figure 8 shows a schematical view of a sixth example where there is a mobile node in a zone of a gateway node; and Figure 9 shows a schematical view of the sixth example where there are two mobile nodes in a zone of a gateway node. DETAILED DESCRIPTION

With reference to Figure 1 , there is a first example of a wireless communication system 1 comprising a first mobile node arrangement 2a that is carried by a first vehicle 6a that travels along a track 4, where the first vehicle 6a according to some aspects is constituted by a train where there is a plurality of passengers that require Internet access, and where the track 4 is constituted by a railway track 4. Here, the track 4 is running along a west direction W and an opposing east direction E, and the first vehicle 6a is running in the east direction E.

There is a plurality of fixed nodes 3a, 3b, 3c, 3d, 3e, 3f arranged along the track 4 and are adapted to cover a corresponding zone 5a, 5b, 5c, 5d, 5e, 5f. The zones 5a, 5b, 5c, 5d, 5e, 5f are constituted by geographical zones that each covers a corresponding section of the track 4. Each fixed node 3a, 3b, 3c, 3d, 3e, 3f is adapted to communicate with its adjacent fixed node or nodes, where two nodes 3a, 3f constitute gateway nodes 3a, 3f which are connected to a core network 7a, 7f. The other fixed nodes 3b, 3c, 3d, 3e constitute intermediate nodes 3b, 3c, 3d, 3e. In this context, the term adjacent means that are no other fixed nodes positioned between two adjacent fixed nodes.

Each gateway node 3a, 3f comprises a corresponding gateway antenna arrangement 12, 13 (only indicated in Figure 1 and Figure 2), each intermediate node 3b, 3c, 3d,

3e comprises a corresponding intermediate antenna arrangement 14 (only one indicated in Figure 1 and Figure 2 for reasons of clarity), and each mobile node arrangement 2a comprises a corresponding mobile antenna arrangement 15 (only one indicated in Figure 1 for reasons of clarity).

According to the present disclosure, the mobile node arrangement 2a is adapted to replace a fixed node 3b while at least partly being present in the corresponding zone 5b. In the example according to Figure 1 , there is a first gateway node 3a that is connected to a first core network 7a and is adapted to cover a corresponding first gateway zone 5a, and a second gateway node 3f that is connected to a second core network 7f and is adapted to cover a second gateway zone 5b. There is furthermore a first intermediate node 3b, a second intermediate node 3c, a third intermediate node 3d and a fourth intermediate node 3e, adapted to cover a corresponding first intermediate zone 5b, second intermediate zone 5c, third intermediate zone 5d and fourth intermediate zone 5e.

The first vehicle 6a is here present in the first intermediate zone 5b, travelling in a west W direction towards the second intermediate zone 5c, and while being present in the first intermediate zone 5b, the first mobile node arrangement 2a replaces the functionality of the first intermediate node 3b. Data then flow between the first gateway node 3a and the second intermediate node 3c via the first mobile node arrangement 2a.

When the first vehicle 6a enters the second intermediate zone 5c, the first intermediate node 3b resumes its functionality such that its link to the first gateway node 3a is restored, and the first mobile node arrangement 2a then instead replaces the functionality of the second intermediate node 3c. Data then flow between the first intermediate node 3b and the third intermediate node 3d via the first mobile node arrangement 2a. While a functionality of a fixed node is replaced, that fixed node is not used.

More in detail, each fixed node 3a, 3b, 3c, 3d, 3e, 3f is adapted to communicate via a first communication resource Ri and a second communication resource R2. Each fixed node 3b, 3c, 3d, 3e that has two adjacent fixed nodes 3a, 3b, 3c, 3d, 3e, 3f is arranged to transmit signals to a first adjacent fixed node and to receive signals from a second adjacent fixed node via either the first communication resource R1 or the second communication resource R2, and to transmit signals to the second adjacent fixed node and to receive signals from the first adjacent fixed node via the other of said communication resources R1, R2. As shown in Figure 1 , the first gateway node 3a is adapted to transmit signals to the first intermediate node 3b via the first communication resource Ri, and to receive signals from the first intermediate node via the second communication resource R2. Correspondingly, the first intermediate node 3b is adapted to receive signals from the first gateway node 3a via the first communication resource R1, and to transmit signals to the first gateway node 3a via the second communication resource R2.

Furthermore, the first intermediate node 3b is adapted to transmit signals to the second intermediate node 3c via the second communication resource R2, and to receive signals from the second intermediate node via the first communication resource R1. Correspondingly, the second intermediate node 3c is adapted to receive signals from the first intermediate node 3b via the second communication resource R2, and to transmit signals to the first intermediate node 3b via the first communication resource R1.

This continues in this alternatingly repetitive manner along all the fixed nodes 3a, 3b, 3c, 3d, 3e, 3f.

In the example in Figure 1 , when the first mobile node arrangement 2a replaces the functionality of the first intermediate node 3b, the first mobile node arrangement 2a is adapted to receive signals from the first gateway node 3a via the first communication resource R1, to transmit signals to the first gateway node 3a via the second communication resource R2, to transmit signals to the second intermediate node 3c via the second communication resource R2, and to receive signals from the second intermediate node via the first communication resource R1 such that the data channel is maintained. Every time the first mobile node arrangement 2a enters a new zone 5a, 5b, 5c, 5d the communication resources R1 R2 for transmission and reception are swapped with the aim of reducing interference. A communication resource is a generic terms, where in this context a communication resources comprises at least one of a frequency channel, a time slot and/or a coded channel. In other words, a communication resource can according to some aspects comprise only a frequency channel, or a mix of a frequency channel and a time slot. This means that frequency division multiplexing (FDD) as well as time division multiplexing (TDD) and Code Division Multiple Access (CDMA) can be used as well. In the case of TDD, only one frequency is required between each radio since duplex transmission is obtained by different time slots for east and west communication between each radio.

Other mixes and variations are of course conceivable within the present technical field. More communication resources than those two sets of communication resources Ri R2 discussed can be introduced in order to reduce interference between the fixed nodes 3a, 3b, 3c, 3d, 3e, 3f, examples will be discussed later.

According to some aspects, wireless communication system 1 that for example operates at a frequency band around 60 GHz has a plurality of fixed nodes 3a, 3b, 3c, 3d, 3e, 3f that function as multiple repeater stations and are built along the track 4 such that the track 4 is covered in both directions W, E. While the first vehicle 6a is present within a zone 5a, 5b, 5c, 5d, 5e, 5f, communication between the first mobile node arrangement 2a and a core network 7a, 7f is enabled by means of an onboard switch or router. According to some aspects, the first mobile node arrangement 2a choose to communicate with one of the core networks 7a, 7b, via the corresponding gateway node 3a, 3f, in dependence of various performance metrics, i.e. the best route is chosen based on current network performance. According to some aspects, it is also possible to in principle double the capacity by using both core networks 7a, 7b. The zone range depends on the geometries of the track 4, according to some aspects, for a 60 GHz network each zone should approximately be between 100 - 1000 m in order to provide reliable capacity and coverage.

With reference to Figure 2, showing a second example, there is a first mobile node arrangement 2a and a second mobile node arrangement 2b in the same zone, here the first intermediate zone 5b. Each mobile node arrangement 2b is carried by a corresponding first vehicle 6a and second vehicle 6b. Previously, when the second mobile node arrangement 2b was present in the second intermediate zone 5c, the first mobile node arrangement 2a was communicating in the east direction E via the second mobile node arrangement 2b, and the second mobile node arrangement 2b was communicating in the west direction W via the first mobile node arrangement 2a. The first mobile node arrangement 2a can also have been communicating in the west direction W, and the second mobile node arrangement 2b can also have been communicating in the east direction E via the fixed nodes. The first mobile node arrangement 2a travels in the east direction E, enters the first intermediate zone 5b and replaces the first intermediate node 3b. When the second mobile node arrangement 2b that travels in the west direction E enters the first intermediate zone 5b, the first mobile node arrangement 2a must turn off the communication directed towards the second intermediate zone 5c, in the east direction E, and let the second mobile node arrangement 2b use the corresponding communication resources Ri, R2 for communication directed towards the second intermediate zone 5c, in the east direction E. Correspondingly, when the second mobile node arrangement 2b that travels in the west direction E enters the first intermediate zone 5b, the second mobile node arrangement 2a must turn off the communication directed towards the first gateway zone 5a, in the west direction W, and let the first mobile node arrangement 2a use the corresponding communication resources R1, R2 for communication directed towards the first gateway zone 5a, in the west direction W. This means that the first mobile node arrangement 2a is connected to the first core network 7a and the second mobile node arrangement 2b is connected to the second core network 7f. When the mobile node arrangement 2a, 2b pass each other, they switch communication directions, such that the first mobile node arrangement 2a is connected to the second core network 7f and the second mobile node arrangement 2b is connected to the first core network 7a.

Generally, when the first mobile node arrangement 2a and the second mobile node arrangement 2b are in a common zone 5b, 5c, 5d, 5e that belongs to an intermediate node 3b, 3c, 3d, 3e, each mobile node arrangement 2a, 2b is adapted to communicate with a fixed node 3a, 3b, 3c, 3d, 3e, 3f that is positioned closer to itself than the other mobile node arrangement 2b, 2a. With reference to Figure 3, when more than two mobile node arrangements must be present in common zone, two more communication resources R3, R4 can be allocated. In this example there are three mobile node arrangements in the first intermediate zone 5b at the same time, a first mobile node arrangement 2a, a second mobile node arrangement 2b and a third mobile node arrangement 2c that is positioned between the first mobile node arrangement 2a and the second mobile node arrangement 2b.

Here the first mobile node arrangement 2a communicates towards the first gateway zone 5a, in the west direction W, and the second mobile node arrangement 2b communicates towards the second intermediate zone 5c, in the east direction E as described above with reference to Figure 2. In this way, the first intermediate zone 5b is split between the two mobile node arrangements 2a, 2b.

The first mobile node arrangement 2a and the second mobile node arrangement 2b communicate with each other via the third mobile node arrangement 2c via a third communication resource R3 and a fourth communication resource R4. The third communication resource R3 is used for communication in the east direction E, and the fourth communication resource R4 is used for communication in the west direction W.

When the mobile node arrangements 2a, 2b, 2c shift positions in the zone 5b, their communication change correspondingly, such that the mobile node arrangements that are closest to a fixed node adapted to cover another zone communicate with that fixed node via the first communication resource R1 and the second communication resource R2, and with the closest mobile node arrangement in the zone 5b via the third communication resource R3 and the fourth communication resource R4. That mobile node arrangement that is positioned between other mobile node arrangements in the zone 5b communicate with these via the third communication resource R3 and the fourth communication resource R4. There can be more than one mobile node arrangement that is positioned between other mobile node arrangements in the zone 5b, but all these communicate with these via the third communication resource R3 and the fourth communication resource R4.

Since the mobile node arrangements 2a, 2b, 2c are relatively close to each other, the communication between the mobile node arrangements 2a, 2b, 2c can operate with a relatively lower power compared to the other links. Using the third communication resource R3 and the fourth communication resource R4 for communication between mobile node arrangements in a common zone can also be applied in the example described with reference to Figure 2 where there are only two mobile node arrangements in a common zone. This enables communication to flow in both directions, such that none of the mobile node arrangements is limited to a certain gateway node; this is illustrated in Figure 5, which also illustrated a fourth example that will be discussed below.

Generally, when there are at least two mobile node arrangements 2a, 2b, 2c in a common zone 5a, 5b, 5c, 5d, 5e, 5f, these mobile node arrangements 2a, 2b, 2c are adapted to communicate with each other via a communication resources R3, R4 that differ from the communication resources R1, R2 used for communication with adjacent fixed nodes adapted to cover other zones.

In a fourth example, a situation where two mobile node arrangements meet each other within a zone in two different zones at the same time will be discussed with reference to Figure 4, Figure 5 and Figure 6.

In Figure 4, there is a first mobile node arrangement 2a and a second mobile node arrangement 2b that are present in the first intermediate zone 5b at the same time, meeting each other, and there is a third mobile node arrangement 2c and a fourth mobile node arrangement 2d that are present in the fourth intermediate zone 5e at the same time, also meeting each other. The first mobile node arrangement 2a that travels in the east direction E communicates with the first gateway node 3a, and the fourth mobile node arrangement 2d that travels in the west direction W communicates with the second gateway node 3f.

However, since there is no network connection present between the mobile node arrangement 2a and the fourth mobile node arrangement 2d, all data connection will be lost for the second mobile node arrangement 2b and the third mobile node arrangement 2c. In order confer data connection for the second mobile node arrangement 2b and the third mobile node arrangement 2c, the communication between mobile node arrangements as discussed above with reference to Figure 3 will be used here as well. This will be discussed more in detail below.

Figure 5 shows the first mobile node arrangement 2a and that second mobile node arrangement 2b that are approaching each other in the first intermediate zone 5b. The mobile node arrangements communicate with a respective fixed node 3a, 3c via the first communication resource Ri and the second communication resource R2, and with each other vi the third communication resource R3 and the fourth communication resource R4.

More in detail, the first mobile node arrangement 2a transmits signals to the first gateway node 3a via the second communication resource R2, and transmits signals to the second mobile node arrangement 2b via the third communication resource R3. The first mobile node arrangement 2a receives signals from the first gateway node 3a via the first communication resource R1, and receives signals from the second mobile node arrangement 2b via the fourth communication resource R4.

Correspondingly, the second mobile node arrangement 2b transmits signals to the second intermediate node 3c via the second communication resource R2, and transmits signals to the first mobile node arrangement 2a via the fourth communication resource R4. The second mobile node arrangement 2b receives signals from the second intermediate node 3c via the first communication resource R1, and receives signals from the first mobile node arrangement 2a via the third communication resource R3. When the trains have passed each other and still are present in the first intermediate zone 5b as shown in Figure 6, their roles regarding transmission and reception have switched. The same applies for all mobile node arrangements that meet in a common zone, such as the third mobile node arrangement 2c and the fourth mobile node arrangement 2d in Figure 4.

By means of the above, bidirectional data transmission is maintained for all mobile node arrangements, even when two or more mobile node arrangements meet in a common zone for one or more zones at the same time.

According to some aspects, it is assumed that all antenna arrangements 12, 13, 14, 15 comprises antennas that have relatively high directivity for each communication resource which improves system gain and avoid interference. Flowever, the antenna beams of each fixed nodes 3a, 3b, 3c, 3d, 3e, 3f must still cover the track 4 all the way to the next fixed node.

According to some aspects, the gateway antenna arrangements 12, 13 and the intermediate antenna arrangements 14 comprise steerable antennas to further improve system gain between the mobile node arrangement and the fixed nodes. In this case, the steerable antenna follows a mobile node arrangement when applicable. When there is no mobile node arrangement in a zone, the steerable antenna is directed to the next adjacent fixed node.

According to some aspects, the mobile antenna arrangements 14 also comprises highly directive antennas or omnidirectional antennas. In case of directive antennas comprised in the mobile antenna arrangements 14, forward facing antennas are used for communication until the mobile node arrangements pass each other. After passing each other, the mobile node arrangements communicate with rear facing antennas. In principle omnidirectional antennas can be used for communication between mobile antenna arrangements; then no antenna switching is necessary. A situation where a mobile node arrangement is passing a gateway node will be discussed in a fifth example with reference to Figure 7 that shows a first mobile node arrangement 2a approaching the first gateway zone 5a. In principle, the same process can be used as described in the first example when the first mobile node arrangement 2a is entering into the first gateway zone 5a that is covered by the first gateway node 3a.

However, since the first mobile node arrangement 2a then will replace the gateway node 3a, the wireless communication system 1 will lose connection to the first core network 7a. This can be acceptable if there are several other gateway nodes in the wireless communication system, enabling data traffic to be in operation in both east direction E and west direction W. However, capacity will be lost since one connection to the core network will be gone while the first mobile node arrangement 2a is in the first gateway zone 5a.

According to some aspects, the first mobile node arrangement 2a is not allowed to replace the gateway node 3a and then the first mobile node arrangement 2a will lose its data connection while being in the first gateway zone 5a. The rest of the wireless communication system 1 will then still have full capacity as usual. Provided that the first gateway zone 5a is relatively small, this constitutes be an acceptable solution. According to some aspects, the gateway antenna arrangements 12, 13 comprises steerable antennas which can minimize the time the first mobile node arrangement 2a will lose its data connection by temporarily changing the effective size of the corresponding gateway zone.

Generally this means that each gateway node 3a, 3f is adapted to maintain communication with its adjacent nodes when one or more mobile node arrangements are present in the corresponding zone 5a, 5f, such that each one of said mobile node arrangements is adapted to terminate all communication while being present within the corresponding zone 5a, 5f.

According to some aspects, with reference to Figure 8 showing a sixth example, in analogy with the third example discussed above, further radio resources R3, R4 can be used for communication between the first mobile node arrangement 2a and the adjacent intermediate nodes 11 , 3b while the first mobile node arrangement 2a is present within the first gateway zone 5a. More in detail, while the first mobile node arrangement 2a is present within the first gateway zone 5a, the first gateway node 7a continues to function as before, but the first mobile node arrangement 2a terminates the use of the ordinary radio resources Ri, R2 used until then. Instead, other radio resources, here a third radio resource R3 and a fourth radio resources R4, are switched on instead.

The first mobile node arrangement 2a transmits signals to the adjacent fixed nodes; a further intermediate node 11 adapted to cover a corresponding zone 10 and the first intermediate node 3b via the third communication resource R3, and receives signals from these fixed nodes 11 , 3b via the fourth communication resource R4. The first gateway node 3a communicates with the adjacent fixed nodes 11 , 3b via the ordinary radio resources R1, R2 without change, not being affected by the passing first mobile node arrangement 2a.

If there is only one mobile node arrangement in a gateway zone, bi-directional communication is possible. Should there be two mobile node arrangements in a gateway zone, they would communicate with the closest adjacent fixed node via the third radio resource R3 and the fourth radio resource R4 as shown for the first mobile node arrangement 2a and a second mobile node arrangement 2b travelling in the west direction W in Figure 9.

Generally, this means hat when at least one mobile node arrangement 2a, 2b is present in a common zone 5a, 5f that belongs to a gateway node 3a, 3f, each mobile node arrangement 2a, 2b that is closer to an adjacent fixed node 11 , 5b than any other mobile node arrangement is said zone 5a, 5f is adapted to communicate with said adjacent fixed node 11 , 5b via a third communication resource R3 and a fourth communication resource R4 while the gateway node 3a, 3f communicates with the adjacent fixed node 11 , 5b via other communication resources R1, R2, here the first communication resource R1 and the second communication resource R2. This enables two mobile node arrangements 2a, 2b to be in a gateway zone 5a, 5f with connectivity to all mobile node arrangements 2a, 2b in all zones. It is required that the adjacent nodes 11 , 5b are adapted for communicating via the third communication resource R3 and the fourth communication resource R4. Alternatively, according to some aspects, instead the gateway nodes 3a, 3f is adapted for communicating via the third communication resource R3 and the fourth communication resource R4. This simplifies installation, but allows only one mobile node arrangement 2a at a time in a gateway zone 5a, 5f. The mobile antenna arrangements 14 then suitably comprise an omnidirectional antenna.

The signaling between mobile node arrangements and the fixed nodes 3a, 3b, 3c, 3d, 3e, 3f in order to facilitate a mobile node’s replacement of a fixed node can be implemented in a number of different ways. According to some aspects, the fixed nodes 3a, 3b, 3c, 3d, 3e, 3f are adapted to identify an approaching mobile node arrangements e.g. by detection of increased interference, or by a special signaling format causing the fixed node in question to turn off its transmitters. The set-up of the vehicle-to-vehicle radios can be run independently of the longer microwave links since they use their own frequencies. According to some aspects, either a centralized management system 16 can be adapted to provide hand-over information; alternatively, the fixed nodes 3a, 3b, 3c, 3d, 3e, 3f are adapted to work autonomously without the need for central management.

Several examples have been discussed above, disclosing a wireless communication system 1 that can handle maximum one mobile node arrangement per zone with connections to both gateway nodes, where two mobile node arrangements can be in one zone, e.g. when they meet or pass, splitting the connection such that one mobile node arrangement communicates through the first gateway node 3a and the other mobile node arrangement communicates through the second gateway node 3f. More mobile node arrangements can be accommodated in one zone by the introduction of additional communication resources. The present disclosure also relates to a mobile node arrangement 2a, 2b adapted to travel along a track 4 and to communicate with adjacent fixed nodes 3a, 3b, 3c, 3d, 3e, 3f among a plurality of fixed nodes 3a, 3b, 3c, 3d, 3e, 3f arranged along a track 4 and adapted to cover a corresponding zone 5a, 5b, 5c, 5d, 5e, 5f, wherein said mobile node arrangement 2a, 2b is adapted to replace at least one fixed node 3b while at least partly being present in the corresponding zone 5b.

The present disclosure also relates to a method for maintaining communication between at least one mobile node arrangement 2a, 2b and a core network 7a, 7f using a plurality of fixed nodes 3a, 3b, 3c, 3d, 3e, 3f arranged along a track 4 and used to cover a corresponding zone 5a, 5b, 5c, 5d, 5e, 5f, along which track 4 at least one mobile node arrangement 2a, 2b, is adapted to travel. Each fixed node 3a, 3b, 3c, 3d, 3e, 3f is used for communicating with its adjacent fixed node or nodes, where at least one fixed node 3a, 3f constitutes a gateway node 3a, 3f that is connected to a core network 7a, 7f and the other fixed nodes 3b, 3c, 3d, 3e constitute intermediate nodes 3b, 3c, 3d, 3e. The method comprises replacing at least one fixed node 3b with at least one mobile node arrangement 2a, 2b while said mobile node arrangement 2a, 2b at least partly is present in the corresponding zone 5b.

The present disclosure is not limited to the examples above, but may vary freely within the scope of the appended claims. For example, each antenna arrangements 12, 13, 14, 15 having a certain coverage, which does not have to lie in an azimuth plane, by may lie in any suitable plane, such as for example an elevation plane. The corresponding antenna beams can be single or dual polarized.

The examples provided with certain mobile node arrangements and certain communication resources are only provided in order to clearly explain how the present disclosure can be implemented. Many other examples are of course possible, where the number of fixed nodes and the distribution of gateway nodes along the track varies. There can be any number of communication resources used in the wireless communication system 1 , the more different communication resources that are used for communication, the more interference between nodes is reduced. This is of course in dependence of the resources available in and for the wireless communication system 1.

Generally, the present disclosure relates to a wireless communication system 1 comprising at least one mobile node arrangement 2a, 2b and a plurality of fixed nodes 3a, 3b, 3c, 3d, 3e, 3f arranged along a track 4 and adapted to cover a corresponding zone 5a, 5b, 5c, 5d, 5e, 5f, along which track 4 at least one corresponding mobile node arrangement 2a, 2b is adapted to travel, where each fixed node 3a, 3b, 3c, 3d, 3e, 3f is adapted to communicate with its adjacent fixed node or nodes, where at least one fixed node 3a, 3f constitutes a gateway node 3a, 3f that is connected to a core network 7a, 7f and the other fixed nodes 3b, 3c, 3d, 3e constitute intermediate nodes 3b, 3c, 3d, 3e, wherein each mobile node arrangement 2a, 2b is adapted to replace at least one fixed node 3b while at least partly being present in the corresponding zone 5b.

According to some aspects, when there are a first mobile node arrangement 2a and second mobile node arrangement 2b in a common zone 5b, 5c, 5d, 5e that belongs to an intermediate node 3b, 3c, 3d, 3e, each mobile node arrangement 2a is adapted to communicate with a fixed node 3a, 3b, 3c, 3d, 3e, 3f that is positioned closer to itself than the other mobile node arrangement 2b.

According to some aspects, each fixed node 3a, 3b, 3c, 3d, 3e, 3f is adapted to communicate via a first communication resource Ri and a second communication resource R2 such that each fixed node 3b, 3c, 3d, 3e having two adjacent fixed nodes 3a, 3b, 3c, 3d, 3e, 3f is arranged to transmit signals to a first adjacent fixed node and to receive signals from a second adjacent fixed node via either the first communication resource Ri or the second communication resource R2, and to transmit signals to the second adjacent fixed node and to receive signals from the first adjacent fixed node via the other of said communication resources R1, R2. According to some aspects, each mobile node arrangement 2a, 2b, 2c is arranged to communicate also via communication resources R3, R4 that differ from the first communication resource R1 or the second communication resource R2.

According to some aspects, when at least one mobile node arrangement 2b is present in a common zone 5a, 5f that belongs to a gateway node 3a, 3f, each mobile node arrangement 2b that is closer to an adjacent fixed node 11 , 5b than any other mobile node arrangement in said zone 5a, 5f is adapted to communicate with said adjacent fixed node 11 , 5b via communication resources R3, R4 that differ from the communication resources R3, R4 via which the gateway node 3a, 3f is adapted to communicate with the adjacent fixed nodes 11 , 5b.

According to some aspects, when there are at least two mobile node arrangements 2a, 2b, 2c in a common zone 5a, 5b, 5c, 5d, 5e, 5f, these mobile node arrangements 2a, 2b, 2c are adapted to communicate with each other via communication resources R3, R4 that differ from the communication resources R1, R2 used for communication with adjacent fixed nodes adapted to cover other zones.

According to some aspects, each gateway node 3a, 3f is adapted to maintain communication with its adjacent nodes when one or more mobile node arrangements are present in the corresponding zone 5a, 5f, such that each one of said mobile node arrangements is adapted to terminate all communication while being present within the corresponding zone 5a, 5f.

According to some aspects, at least one gateway node 3a, 3f comprises an electrically steerable antenna arrangement 12, 13.

According to some aspects, at least one communication resources R1, R2, R3, R4 at least comprises a frequency channel. According to some aspects, at least one communication resources Ri, R2, R3, R4 at least comprises a time slot. According to some aspects, at least one communication resources R1, R2, R3, R4 at least comprises a coded channel.

According to some aspects, there are different communication resources between at least two adjacent pairs of fixed nodes 3a, 3b, 3c, 3d, 3e, 3f.

Generally, the present disclosure also relates to a mobile node arrangement 2a, 2b adapted to travel along a track 4 and to communicate with adjacent fixed nodes 3a, 3b, 3c, 3d, 3e, 3f among a plurality of fixed nodes 3a, 3b, 3c, 3d, 3e, 3f arranged along a track 4 and adapted to cover a corresponding zone 5a, 5b, 5c, 5d, 5e, 5f, wherein said mobile node arrangement 2a, 2b is adapted to replace at least one fixed node 3b while at least partly being present in the corresponding zone 5b.

According to some aspects, when the mobile node arrangement 2a is in a zone 5b, 5c, 5d, 5e together with another mobile node arrangement 2b, the mobile node arrangement 2a is adapted to communicate with a fixed node 3a, 3b, 3c, 3d, 3e, 3f that is positioned closer to itself than the other mobile node arrangement 2b.

Generally, the present disclosure also relates to a method for maintaining communication between at least one mobile node arrangement 2a, 2b and a core network 7a, 7f using a plurality of fixed nodes 3a, 3b, 3c, 3d, 3e, 3f arranged along a track 4 and used to cover a corresponding zone 5a, 5b, 5c, 5d, 5e, 5f, along which track 4 at least one mobile node arrangement 2a, 2b is adapted to travel, where each fixed node 3a, 3b, 3c, 3d, 3e, 3f is used for communicating with its adjacent fixed node or nodes, where at least one fixed node 3a, 3f constitutes a gateway node 3a, 3f that is connected to a core network 7a, 7f and the other fixed nodes 3b, 3c, 3d, 3e constitute intermediate nodes 3b, 3c, 3d, 3e, wherein the method comprises replacing at least one fixed node 3b with at least one mobile node arrangement 2a, 2b while said mobile node arrangement 2a, 2b at least partly is present in the corresponding zone 5b.

According to some aspects, when there are a first mobile node arrangement 2a and second mobile node arrangement 2b in a common zone 5b, 5c, 5d, 5e that belongs to an intermediate node 3b, 3c, 3d, 3e, each mobile node arrangement 2a is used for communicating with a fixed node 3a, 3b, 3c, 3d, 3e, 3f that is positioned closer to itself than the other mobile node arrangement 2b. According to some aspects, each fixed node 3a, 3b, 3c, 3d, 3e, 3f uses a first communication resource Ri and a second communication resource R2 for communication such that each fixed node 3b, 3c, 3d, 3e having two adjacent fixed nodes 3a, 3b, 3c, 3d, 3e, 3f uses either the first communication resource R1 or the second communication resource R2 for transmitting signals to a first adjacent fixed node and to receive signals from a second adjacent fixed node, and uses the other of said communication resources R1, R2 for transmitting signals to the second adjacent fixed node and to receive signals from the first adjacent fixed node.

According to some aspects, each mobile node arrangement 2a, 2b, 2c uses communication resources R3, R4 that differ from the first communication resource R1 or the second communication resource R2.

According to some aspects, at least one mobile node arrangement 2b is present in a common zone 5a, 5f that belongs to a gateway node 3a, 3f, each mobile node arrangement 2b that is closer to an adjacent fixed node 11 , 5b than any other mobile node arrangement in said zone 5a, 5f uses communication resources R3, R4 that differ from the communication resources R3, R4 via which the gateway node 3a, 3f is adapted to communicate with the adjacent fixed nodes 11 , 5b for communicating with said adjacent fixed node 11 , 5b.

According to some aspects, when there are at least two mobile node arrangements 2a, 2b, 2c in a common zone 5a, 5b, 5c, 5d, 5e, 5f, these mobile node arrangements 2a, 2b, 2c use via communication resources R3, R4 that differ from the communication resources Ri, R2 used for communication with adjacent fixed nodes adapted to cover other zones when communicating with each other.

According to some aspects, each gateway node 3a, 3f maintains communication with its adjacent nodes when one or more mobile node arrangements are present in the corresponding zone 5a, 5f, such that each one of said mobile node arrangements terminates all communication while being present within the corresponding zone 5a, 5f. According to some aspects, at least one gateway node 3a, 3f uses an electrically steerable antenna arrangement 12, 13.

According to some aspects, at least one communication resources R1, R2, R3, R4 at least uses a frequency channel.

According to some aspects, at least one communication resources R1, R2, R3, R4 at least uses a time slot.

According to some aspects, at least one communication resources R1, R2, R3, R4 at least uses a coded channel.

According to some aspects, there are different communication resources between at least two adjacent pairs of fixed nodes 3a, 3b, 3c, 3d, 3e, 3f.