WO2013100755A1

WO2013100755A1 - A wireless communication system

Info

Publication number: WO2013100755A1
Application number: PCT/MY2012/000172
Authority: WO
Inventors: Azmi Yaacob; Hafizal BIN MOHAMAD @ DIN; Nordin BIN RAMLI; Ahmad Zaki BIN ABU BAKAR; Wahidah Binti HASHIM
Original assignee: Mimos Bhd
Current assignee: Mimos Bhd
Priority date: 2011-12-29
Filing date: 2012-06-29
Publication date: 2013-07-04
Anticipated expiration: 2014-06-29
Also published as: MY161005A

Description

A WIRELESS COMMUNICATION SYSTEM

FIELD OF INVENTION

The present invention relates to a wireless communication system and more particularly to a wireless communication system having multiple antenna configuration for use in a wireless mesh network.

BACKGROUND OF THE INVENTION

IEEE 802.11 is a set of standards for implementing wireless local area network (WLAN) computer communication in frequency bands of 2.4 GHz, 3.6 GHz and 5 GHz. IEEE 802.1 1s extends those standards for wireless mesh networking by defining an extended service set (ESS) of a number of interconnected devices or nodes to enable automatic topology learning and dynamic path configuration. Referring now to FIG. 1 , a wireless mesh network (WMN) generally comprises of mesh routers (10), mesh clients (20) and a mesh portal (30). Each node is capable to operate both as a host and as a router that can provide packet forwarding on behalf of another node that is out of range of transmission with its destination. Moreover, each node supports mesh functions such as neighbour discovery, channel selection and association forming with its neighbouring nodes. The mesh routers (10) are interconnected through wireless connection. The mesh clients (20) are connected to the mesh routers (10) through either an Ethernet interface or the same radio technology as the mesh routers (10). The mesh portal (30) is connected to the mesh routers for connecting to other wired or wireless network. For instance, the mesh portal (30) is further connected to a gateway (40) for Internet connection.

However, the current routing and Media Access Control (MAC) protocols limit the capacity, quality of service and capabilities of WMN and thus, enhancements are made to the MAC protocol. Such MAC enhancements include Mesh Coordinated Channel Access (MCCA) which is a distributed reservation protocol that allows mesh routers to avoid frame collisions. MCCA is an optional protocol in the IEEE 802.1 1s standard. In another effort to increase the network capacity of WMN, the mesh router is equipped with multiple antennas to support multiple 802.1 1 radios for deploying a multi-radio mesh network whereby a unique frequency is used for each wireless hop. FIG. 2 shows network architecture of the mesh router equipped with multiple antennas (110). The mesh router includes a MAC layer (120) which comprises of MAC scheduler and QoS policy module (121), mesh topology and routing module (122), and a medium access coordination module (123). The MAC layer (120) is connected to multiple physical layers (130). Each physical layer (130) is further connected to a power amplifier (140) which is coupled to an antenna (110) dedicated for a particular radio. Therefore, for N number of radio to be used in multi-radio mesh network, N number of physical layer (130), power amplifier (140) and antenna (110) are required for the mesh router.

However, the usage of multiple radios and power amplifiers of the mesh router is a waste or inefficient for lightly loaded node or network. Moreover, such mesh router cannot be used for single-radio mesh network.

Therefore, there is a need to provide a wireless communication system that addresses the abovementioned drawbacks.

SUMMARY OF INVENTION

The present invention provides a wireless communication system for use in a wireless mesh network. The system comprises of at least three antennas (210, 310), a Media Access Control (MAC) layer (220, 320), at least one physical layer (230, 330), at least one power amplifier (240, 340), an antenna selection module (250, 350) and a synchronization module (260, 360). The MAC layer (220, 320) is connected to the at least one physical layer (230, 330) and the synchronization module (240, 340). The MAC layer (220, 320) includes a MAC scheduler and QoS policy module (221 , 321), a mesh configuration and management module (222, 322), and a Mesh Coordinated Channel Access (MCCA) module (223, 323). The at least one power amplifier (240, 340) is connected to the at least one physical layer (230, 330) and the antenna selection module (250, 350). The antenna selection module (250, 350) is further connected to the at least three antennas and the synchronization module (260, 360). Preferably, the at least three antennas (210, 310) include at least one omnidirectional antenna, and at least two directional antennas.

Preferably, the number of antennas (210, 310) used is based on M > N + 2, where M is a number of antennas (210, 310), and N is a number of radios.

The present invention also provides a method for operating a wireless communication system in a wireless mesh network. The method is characterised by the steps of determining number of radio and antenna within the wireless communication system by a mesh coordinated channel access (MCCA) module (223, 323); performing a coordinated channel access sub-process; creating and updating a resource allocation table based on the information from an antenna node assignment table by the MCCA module (223, 323); synchronizing the MCCA module (223, 323) and an antenna selection module (250, 350) by a synchronization module (260, 360); assigning each antenna (210, 310) for different neighbouring nodes by the antenna selection module (250, 350); and transmitting and receiving data from neighbouring nodes.

Preferably, the coordinated channel access sub-process comprising the steps of activating the antennas (210, 310) to receive beacon signal from neighbouring nodes; receiving beacon signal from a neighbouring node; locating a source node of the beacon signal; sending a peering request to the identified source node; establishing a mesh peering link with the identified source node; and storing location and direction information of the identified source node in an antenna node assignment table. Moreover, the step of establishing a mesh peering link suitably includes receiving an acknowledgement from the identified source node. Preferably, synchronizing the MCCA module (223, 323) and the antenna selection module (250, 350) by the synchronization module (260, 360) comprises the steps of initializing a timing reference entity; reading and verifying validity of clock from the timing reference entity by the MCCA module (223, 323) and the antenna selection module (250, 350); synchronizing timer of the MCCA module (223, 323) and the antenna selection module (250, 350) with the timing reference entity; sending test frames with timestamp from the MCCA module (223, 323) to the antenna selection module (250, 350); comparing the timestamp on the test frames with the time it received the test frames by the antenna selection module (250, 350); and instructing the MCCA module (223, 323) to speed up or slow down transmission rate by the antenna selection module (250, 350) if the timestamp differs from the time the antenna selection module (250, 350) received the test frames.

Preferably, assigning each antenna (210, 310) for different neighbouring nodes by the antenna selection module (250, 350) includes the steps of sending the resource allocation table from the MCCA module (223, 323) to the antenna selection module (250, 350); comparing the received resource allocation table with a stored resource allocation table by the antenna selection module (250, 350); discarding the received resource allocation table and utilizing the stored resource allocation table if there is no difference between the two resource allocation tables; updating the stored resource allocation table with the received resource allocation table by the antenna selection module (250, 350) if there is a difference between the two resource allocation tables; and selecting an appropriate antenna (210, 310) towards the source nodes by the antenna selection module (250, 350). Preferably, transmitting and receiving data from neighbouring nodes includes the steps of constructing and mapping the resource allocation table based on the antenna nodes assignment table; broadcasting the resource allocation table to neighbouring nodes; and sending the resource allocation table to the antenna selection module (250, 350).

Advantageously, the present invention improves transmission and reception efficiency of a wireless communication system used in a wireless mesh network. Advantageously, the present invention increases network capacity of a wireless mesh network. BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 shows a network diagram of a wireless mesh network.

FIG. 2 shows a network architecture block diagram of a mesh router equipped with multiple antennas.

FIG. 3 shows an architecture diagram of a wireless mesh network.

FIG. 4 shows a network architecture of a wireless communication system in accordance with a first embodiment of the present invention.

FIG. 5 shows a network architecture of a wireless communication system in accordance with a second embodiment of the present invention.

FIGS. 6(a-e) show flowcharts of operating the wireless communication system in accordance with an embodiment of the present invention.

DESCRIPTION OF THE PREFFERED EMBODIMENT

A preferred embodiment of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.

A wireless communication system is provided in the present invention. The wireless communication system is equipped with multiple antennas to work with lower number of radio in a wireless mesh network. More particularly, the wireless communication system uses M-number of antennas to work with /V-number of radio based on M≥ N + 2. Moreover, the wireless communication system includes an enhanced mesh coordinated channel access (MCCA) module to provide reservation of contention free time slots and to map the direction of source and destination nodes in the wireless mesh network. In addition to that, the wireless communication system includes an antenna selection module to select the appropriate antenna to be employed during transmission and reception of data in the wireless mesh network. In order to ensure the synchronization between MCCA module and antenna selection module, a synchronization module is provided in the wireless communication system.

FIG. 3 shows an architecture diagram of a wireless mesh network which comprises of a plurality of nodes. The wireless communication system is used as a node in the wireless mesh network, wherein each node is able to transmit and receive data signal from all different angles of its neighbouring nodes. Moreover, the wireless communication system is able to accommodate concurrent incoming and outgoing signals. For an example, if a first source node (S1) is transmitting data to a first destination node (D1) through several intermediate nodes as depicted by solid arrows, while a second source node (S2) is also transmitting data to a second destination node (D2) through several intermediate nodes as depicted by dashed arrows, an intermediate node (11) is able to efficiently organize and schedule the transmission and reception from its neighbouring nodes.

Referring now to FIG. 4, there is shown a wireless communication system according to a first embodiment of the present invention. The wireless communication system is used as a node in a single-radio wireless mesh network. The wireless communication system comprises of M-number of antennas (210), a Media Access Control (MAC) layer (220), a physical layer (230), a power amplifier (240), an antenna selection module (250) and a synchronization module (260). Moreover, the wireless communication system may include other higher layers (270) that may be apparent to a person skilled in the art. Such higher layers (270) include transport layer, session layer, presentation layer and application layer.

The number of antennas (210) used in the wireless communication system is based on M≥ N + 2, where M is a number of antennas (210), and N is a number of radios. Moreover, the multiple antennas (210) include at least one omni-directional antenna, and at least two directional antennas. The omni-directional antenna is used for receiving beacon from neighbouring nodes, while the directional antennas are used for locating a source beacon and for data transmission between nodes. The MAC layer (220) is connected to the physical layer (230) and the synchronization module (240). The MAC layer (220) further includes a MAC scheduler and QoS policy module (221 ), a mesh configuration and management module (222), and a MCCA module (223). The MAC scheduler and QoS policy module (221) is used to schedule the transmission operation through the antennas and to select quality of service (QoS) based on the underlined policy such as, but not limited to, type of traffics and network capacity. Generally, the main purpose of the MAC scheduler and QoS policy module (221) is for supporting QoS, and increasing the network throughput which includes power management and selection of multi- channel. The mesh configuration and management module (222) is used for handling the mesh topology, layer two routing (path selection) and mesh security. The MCCA module (223) is used to enable the reservation of contention time slots in the wireless mesh network. Moreover, the MCCA module (223) is also used to map the antenna direction of a source node in an antenna node assignment table which is then used for determining the direction of the source node.

The physical layer (230) is connected to the MAC layer (220) and the power amplifier (240). The physical layer (230) is used to define the signal based on type of modulation, forward error correction, and channel coding. Moreover, the physical layer (230) includes a channel equalizer to mitigate the effect of multipath signals.

The power amplifier (240) is used to amplify the transmission and reception signals and it is connected to the physical layer (230) and the antenna selection module (250).

The antenna selection module (250) is connected to the multiple antennas and it selects the appropriate antenna (210) to be employed for transmission and reception in the wireless mesh network. The selection is based on the MCCA module (223). The antenna selection module (250) is also connected to the power amplifier (240) and the synchronization module (260).

The synchronization module (260) is used to provide the timing alignment between the MCCA module (223) and antenna selection module (250) and thus, ensuring timely interaction between the MCCA module (223) and the antenna selection module (250). The synchronization module (260) is connected to the MAC layer (220) and the antenna selection module (250).

Referring now to FIG. 5, there is shown a wireless communication system according to a second embodiment of the present invention. The wireless communication system is used as a node in a multi-radio wireless mesh network. The wireless communication system comprises of M-number of antennas (310), a Media Access Control (MAC) layer (320), A/-number of physical layers (330), N- number of power amplifiers (340), an antenna selection module (350) and a synchronization module (360). Moreover, the wireless communication system may include other higher layers (370) that may be apparent to a person skilled in the art. Such higher layers include transport layer, session layer, presentation layer and application layer. The number of antennas (310) used in the wireless communication system is based on M≥ N + 2, where M is a number of antennas (310), and N is a number of radios. Moreover, the multiple antennas (310) include at least one omni-directional antenna, and at least two directional antennas. The omni-directional antenna is used for receiving beacon from neighbouring nodes, while the directional antennas are used for locating a source beacon and for data transmission between nodes.

The MAC layer (320) is connected to the physical layer (330) and the synchronization module (360). The MAC layer (320) further includes a MAC scheduler and QoS policy module (321), a mesh configuration and management module (322), and a MCCA module (323). The MAC scheduler and QoS policy module (321) is used to schedule the transmission operation through the antennas and to select quality of service (QoS) based on the underlined policy such as, but not limited to, type of traffics and network capacity. Generally, the main purpose of the MAC scheduler and QoS policy module (321) is for supporting QoS, and increasing the network throughput which includes power management and selection of multichannel. The mesh configuration and management module (322) is used for handling the mesh topology, layer two routing (path selection) and mesh security. The MCCA module (323) is used to enable the reservation of contention time slots in the wireless mesh network. Moreover, the MCCA module (323) is also used to map the antenna direction of a source node in an antenna node assignment table which is then used for determining the direction of the source node.

Each physical layer (330) is connected to the MAC layer (320) and a power amplifier (340). The physical layers (330) are used to define the signal based on type of modulation, forward error correction, and channel coding. Moreover, the physical layer (330) includes a channel equalizer to mitigate the effect of multipath signals. Moreover, each physical layer (330) includes a channel equalizer to mitigate the effect of multipath signals.

The power amplifiers (340) are used to amplify the transmission and reception signals. Each power amplifier (340) is connected to a physical layer (330) and the antenna selection module (350). Each power amplifier (340) connected to a physical layer (330) corresponds to a particular radio used.

The antenna selection module (350) is connected to the multiple antennas (310) and it selects the appropriate antenna (310) to be employed for transmission and reception in the wireless mesh network. The selection is based on the MCCA module (323). The antenna selection module (350) is also connected to the power amplifiers (340) and the synchronization module (360).

The synchronization module (360) is used to ensure timely interaction between the MCCA module (323) and the antenna selection module (350). The synchronization module (360) is connected to the MAC layer (320) and the antenna selection module (350).

The operation of the wireless communication system is shown in FIGS. 6. Referring now to FIG. 7a, the MCCA module determines the number of radio and antenna within the wireless communication system as in step 701. Thereon, the wireless communication system performs a coordinated channel access sub-process as in step 702. The coordinated channel access sub-process is to identify all active neighbouring nodes and store information relating to its neighbouring nodes in an antenna node assignment table. In step 703, a resource allocation table is created and updated based on the information from antenna node assignment table by the MCCA module. This is to reserve the time slot for data transmission towards the source node. Table 1 is an example of the resource allocation table.

Table 1

In step 704, the wireless communication system performs a synchronization sub-process to synchronize the timing information provided in the resource allocation table with the antenna selection module. Thereon, in step 705, the wireless communication system performs an antenna selection sub-process by assigning each of its directional antennas toward different neighbouring nodes. The antenna selection sub-process is based on the neighbour node request. In step 706, the wireless communication system performs transmit and receive sub-process for data transmission to/from the wireless communication system from/to its neighbouring nodes. Thereon, the wireless communication system determines whether its neighbouring nodes have transmitted a new request as in decision 707. If a new request exists, then the wireless communication system repeats steps 703 to 706.

Referring now to FIG. 6b, there is shown a flowchart of the coordinated channel access sub-process. Initially, as in step 801 , the omni-directional antenna is activated and waiting to receive beacon from its neighbouring nodes. If there is a request to associate from the neighbouring nodes, the wireless communication system associates with the requested node by trying to locate the source of the beacon via its directional antennas (decision 802 and step 803). Once the wireless communication system has found the source of the beacon, it sends a peering request to the identified source node as in step 804. If source node acknowledges the peering request, then a mesh peering link is established and thereon, the location and direction information of the newly established node is added and updated in an antenna node assignment table (decision 805, and steps 806 to 807). Table 2 is an example of the antenna node assignment table. Table 2

If the source node does not acknowledge the peering request, then a mesh peering link is not established and the wireless communication system randomly tries to associate the failed-to-established source node with a different directional antenna (decision 805, and steps 808 to 809). Steps 803 to decision 805 are then repeated.

Referring now to FIG. 6c, there is shown a flowchart of the synchronization sub-process. A timing reference entity can be of any form of entity to provide a timing reference for the antenna selection module such as a global positioning system (GPS) module, a timer circuit, or a dedicated timing module. Initially, the timing reference entity is initialized and thereon, the MCCA module and antenna selection module read and verify the validity of the clock from the timing reference entity (steps 901 and 902). If the clock value is invalid, the timing reference entity is restarted (decision 903 and step 904) and thereon, steps 901 to 902 are repeated.

If the clock value is valid, then the MCCA module and antenna selection module adjust their own reference timer to be the same as the timing reference entity and thereon, the MCCA module sends test frames with its timestamp on it to the antenna selection module (decision 903 and step 905). In steps 906 and 907, the antenna selection module receives the test frames and compares the timestamp on the test frames with the time it received the test frames. If a clock drift exists, it means there is some delay in the communication line and then, the clock drift is compared with a threshold of clock drift (decision 908 and step 909). If the clock drift is greater than the threshold, the antenna selection module instructs the MCCA module to speed up frame sending and steps 905 to 907 are repeated. If it is lower than the threshold, the antenna selection module instructs the MCCA module to slow down the frame sending and steps 905 to 907 are repeated. However, if no clock drift exists, then the MCCA module and the antenna selection module are synchronized and ready (decision 908 and step 910). Referring now to FIG. 6d, there is shown the antenna selection sub-process of the wireless communication system. In step 1001 , the MCCA module sends the resource allocation table to the antenna selection module. Thereon, in step 1002, the antenna selection module compares the received resource allocation table with a stored resource allocation table. If there is no difference between the two resource allocation tables, then the antenna selection module discards the received resource allocation table and utilizes the stored resource allocation table (decision 1003 and step 1004). If there is a difference between the two resource allocation tables such as but not limited to the source node, destination node, reservation time slot and antenna, then the antenna selection module updates its stored resource allocation table with the received resource allocation table (decision 1003 and step 1005). Thereon in step 1006, the antenna selection module selects the appropriate antenna towards the source nodes by using round robin or fix assignment, or new algorithm that can improve the efficiency and throughput of transmission. Referring now to FIG. 6e, there is shown a flowchart of transmit and receive sub-process of the wireless communication system. If there is any transmission requested from the destination node, the wireless communication system constructs the resource allocation table and maps the resource allocation table with the antenna nodes assignment table (decision 1101 , and steps 1102 to 1103). Thereon, the resource allocation table is broadcasted to its neighbouring nodes as in step 1104. The resource allocation table is also sent to the antenna selection module to select the correct direction towards the requested nodes (1105).

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrated and describe all possible forms of the invention. Rather, the words used in the specifications are words of description rather than limitation and various changes may be made without departing from the scope of the invention.

Claims

1. A wireless communication system for use in a wireless mesh network comprising:

a) at least three antennas (210, 310),

b) a Media Access Control (MAC) layer (220, 320),

c) at least one physical layer (230, 330), and

d) at least one power amplifier (240, 340);

wherein the wireless communication system is characterised in that:

the wireless communication system further includes an antenna selection module (250, 350) and a synchronization module (260, 360), wherein the MAC layer (220, 320) is connected to the at least one physical layer (230, 330) and the synchronization module (260, 360), the at least one power amplifier (240, 340) is connected to the at least one physical layer (230, 330) and the antenna selection module (250, 350), and the antenna selection module (250, 350) is further connected to the at least three antennas (210, 310) and the synchronization module (260, 360); the MAC layer (220, 320) includes a MAC scheduler and QoS policy module (221 , 321), a mesh configuration and management module (222, 322), and a Mesh Coordinated Channel Access (MCCA) module (223, 323).

2. The wireless communication system as claimed in claim 1 , wherein the at least three antennas (210, 310) include at least one omni-directional antenna, and at least two directional antennas.

3. The wireless communication system as claimed in claim 1 , wherein the number of antennas (210, 310) used is based on M≥ N + 2, where M is a number of antennas (210, 310), and N is a number of radios.

4. A method for operating a wireless communication system as claimed in claims 1 to 3 in a wireless mesh network, is characterised by the steps of: a) determining number of radio and antenna within the wireless communication system by a mesh coordinated channel access (MCCA) module (223, 323);

b) performing a coordinated channel access sub-process; c) creating and updating a resource allocation table based on the information from an antenna node assignment table by the MCCA module (223, 323);

d) synchronizing the MCCA module (223, 323) and an antenna selection module (250, 350) by a synchronization module (260, 360);

e) assigning each antenna (210, 310) for different neighbouring nodes by the antenna selection module (250, 350); and

f) transmitting and receiving data from neighbouring nodes.

The method as claimed in claim 4, wherein the coordinated channel access sub-process comprising the steps of:

a) activating the antennas (210, 310) to receive beacon signal from neighbouring nodes;

b) receiving beacon signal from a neighbouring node;

c) locating a source node of the beacon signal;

d) sending a peering request to the identified source node;

e) establishing a mesh peering link with the identified source node; and f) storing location and direction information of the identified source node in an antenna node assignment table.

The method as claimed in claim 5, wherein establishing a mesh peering link includes receiving an acknowledgement from the identified source node.

The method as claimed in claim 4, wherein synchronizing the MCCA module (223, 323) and the antenna selection module (250, 350) by the synchronization module (260, 360) comprising the steps of:

a) initializing a timing reference entity;

b) reading and verifying validity of clock from the timing reference entity by the MCCA module (223, 323) and the antenna selection module (250, 350);

c) synchronizing timer of the MCCA module (223, 323) and the antenna selection module (250, 350) with the timing reference entity;

d) sending test frames with timestamp from the MCCA module (223, 323) to the antenna selection module (250, 350); e) comparing the timestamp on the test frames with the time it received the test frames by the antenna selection module (250, 350); and f) instructing the MCCA module (223, 323) to speed up or slow down transmission rate by the antenna selection module (250, 350) if the timestamp differs from the time the antenna selection module (250, 350) received the test frames.

The method as claimed in claim 4, wherein assigning each antenna (210, 310) for different neighbouring nodes by the antenna selection module (250, 350) includes the steps of:

a) sending the resource allocation table from the MCCA module (223, 323) to the antenna selection module (250, 350);

b) comparing the received resource allocation table with a stored resource allocation table by the antenna selection module (250, 350); c) discarding the received resource allocation table and utilizing the stored resource allocation table if there is no difference between the two resource allocation tables;

d) updating the stored resource allocation table with the received resource allocation table by the antenna selection module (250, 350) if there is a difference between the two resource allocation tables; and e) selecting an appropriate antenna (210, 310) towards the source nodes by the antenna selection module (250, 350).

The method as claimed in claim 4, wherein transmitting and receiving data from neighbouring nodes includes the steps of:

a) constructing and mapping the resource allocation table based on the antenna nodes assignment table;

b) broadcasting the resource allocation table to neighbouring nodes; and c) sending the resource allocation table to the antenna selection module (250, 350).