WO2012150856A1

WO2012150856A1 - A system for channel assignment in a wireless network and a method thereof

Info

Publication number: WO2012150856A1
Application number: PCT/MY2012/000095
Authority: WO
Inventors: Kee Ngoh Ting; Heng Tze David CHIENG
Original assignee: Mimos Berhad
Priority date: 2011-05-04
Filing date: 2012-04-27
Publication date: 2012-11-08
Also published as: MY153784A

Abstract

The present invention is a system of assigning channel in a multi-hop wireless network and a method thereof. The channel assignment includes consideration of interference characteristics of both uplink and downlink direction and channel is assigned based on the least number of interferers.

Description

A SYSTEM FOR CHANNEL ASSIGNMENT IN A WIRELESS NETWORK AND A

METHOD THEREOF FIELD OF THE INVENTION

The present invention relates generally to network communication. More particularly, the invention relates to a system for channel assignment in a multi-hop wireless network and a method thereof.

BACKGROUND OF THE INVENTION

Wireless communication is used to transfer information over a distance. In a wireless environment, interference is a common problem. It causes throughput degradation and communication breakdown. The common types of interferences are co-channel and adjacent-channel interferences. The severity of interference problem is significantly higher in multi-hop environment especially at the wireless backhaul links. This is due to the distances between nodes which are relatively closer in wireless backhaul links. These nodes are located closer to one another to form high quality wireless links.

Radio channel selection is critical to minimize interference but there are only a limited number of non-overlapping channels available. In most parts of the world, IEEE802.1 1 b/g has 13 channels spaced 5 MHz apart (except of a 12 MHz spacing before Channel 14). Since each channel requires 25 MHz of channel separation, the adjacent channels will overlap and interfere with one another. Due to this, only 3 channels are orthogonal of each other and hence recommended to avoid interference. IEEE 802.1 1 a uses the 5GHz band. For most parts of the world it offers at least 12 non- overlapping channels (with potential up to 23 channels). Channel management in multi-hop wireless network is important to ensure optimal network capacity. A bad channel management may result in links experiencing bad quality or suffer constant disconnection. Most of the existing methods of channel assignment do not consider interference experienced by both uplink and downlink direction when deciding on the optimal channel. SUMMARY OF THE INVENTION

It is disclosed herein a system for channel assignment in a wireless network, wherein the system includes: a) at least one interface of at least one first node constructing a means of arranging and perform a channel selection;

wherein the means of arranging data includes one or more available channels information;

wherein the at least one first node is a gateway node or the node which is located nearest to the gateway node; and b) at least one interface of at least one second node in communication with the at least one interface of the at least one first node and sends one or more available channels information to the at least one interface of the at least one first node;

wherein the at least one interface of at the least one first node and the at least one interface of the at least one second node are capable of initiating a channel assignment process and identifying one or more available channels;

wherein the at least one interface of the at least one first node and the at least one interface of the at least one second node switches to the channel selected by the at least one interface of at least one first node and resume communication. It is also disclosed herein, a method for channel assignment in a wireless network, the method includes the steps of: a) initiating a process wherein a default channel is used for communication;

b) initiating a channel assignment process between at least one interface of at least one first node and at least one interface of at least one second node; wherein the at least one first node is a gateway node or the node which is located nearest to the gateway node;

c) identifying one or more available channels by the at least one interface of the at least one first node and the at least one interface of the at least one second node;

d) sending one or more available channels information from the at least one interface of the at least one second node to the at least one interface of the at least one first node;

e) constructing a means of arranging data including one or more available channels information by the at least one interface of the at least one first node;

f) selecting an applicable channel wherein the channel is selected by the at least one interface of the at least one first node;

g) sending the selected channel's information from the at least one first interface of the at least one first node to the at least one interface of the at least one second node;

h) switching of the at least one interface of the at least one first node and the at least one interface of the at least one second node to the selected channel; and i) connecting the at least one interface of the at least one first node and the at least one interface of the at least one second node to resume communication.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates an embodiment of the invention.

Figure 2 illustrates another embodiment of the invention.

Figure 3 illustrates a method of assigning channel in a wireless network.

Figure 4 illustrates message flows for a channel assignment process.

Figure 5 illustrates an example of performing channel selection.

Figure 6 illustrates a method of performing channel selection. DETAILED DESCRIPTION OF THE INVENTION

The invention and its various embodiments are better understood by reading the description along with the accompanying drawings which appear herein for purpose of illustration only and do not limit the invention in any way.

Figure 1 illustrates a multi-hop wireless network which includes a gateway (GW) node (91 ) and one or more subsequent wireless nodes. Each node including GW node (91 ) is equipped with two types of radio interfaces, namely access interface and backhaul interface. Access and backhaul interfaces form access domain and backhaul domain. The two domains may or may not be located in the same frequency band.

There is at least one access interface on each wireless node and the access interface connects wireless devices to a wireless node and subsequently to the wireless multi-hop system and finally to the core network via GW. Wireless devices mentioned herein include but is not limited to fixed, mobile and portable two-way radios, cellular telephones, and personal digital assistants (PDA).

Backhaul interfaces interconnect wireless nodes to form a multi-hop chain topology which connects remote wireless nodes to GW through multi-hopping. There is at least one backhaul interface on each node. A dedicated interface is used to form a wireless link between a two nodes to form a node pair. There could be more than one multi-hop branch from the GW in the network and there could also be sub-branches in a main branch, which forms a tree network.

In the wireless backhaul network, a different channel is assigned to each wireless link by considering both uplink and downlink characteristics. Interferences from internal and external networks are taken into account. Channels are assigned based on the least interfering channel and most balanced channel considering both uplink and downlink characteristics.

Figure 2 illustrates channel assigning between at least one interface (10) of at least one first node (50) and at least one interface (20) of at least one second node (70) wherein the at least one first node (50) is a gateway node (91 ) or the node which is located nearest to the gateway node (91 ).

Figure 3 illustrates a method of assigning channels in a multi-hop network. The method assigning channel in a wireless network includes the steps of: a) initiating a process wherein a default channel is used for communication;

b) initiating a channel assignment process between at least one interface (10) of at least one first node (50) and at least one interface (20) of at least one second node (70);

wherein the at least one first node (50) is a gateway node (91 ) or the node which is located nearest to the gateway node (91 );

c) identifying one or more available channels by the at least one interface (10) of the at least one first node (50) and the at least one interface (20) of the at least one second node (70);

d) sending one or more available channels information from the at least one interface (20) of the at least one second node (70) to the at least one interface (.10) of the at least one first node (50);

e) constructing a means of arranging data including one or more available channels information by the at least one interface (10) of the at least one first node (50); f) selecting an applicable channel wherein the channel is selected by the at least one interface (10) of the at least one first node (50) ;

g) sending the selected channel's information from the at least one first interface (10) of the at least one first node (50) to the at least one interface (20) of the at least one second node (70);

h) switching of the at least one interface (10) of the at least one first node (50) and the at least one interface (20) of the at least one second node (70) to the selected channel; and i) connecting the at least one interface (10) of the at least one first node (50) and the at least one interface (20) of the at least one second node (70) to resume communication. The method further includes checking if there are one or more subsequent interfaces of the first node (50) and/or the second node (70) that requires configuration wherein the process comes to an end if there are no subsequent interfaces to be ^"configured. The method also includes checking if there are more nodes located in the same branch as the first node (50) and/or second node (70) that requires configuration. The method is repeated until all nodes in all branches are configured.

Figure 4 illustrates message flow for a channel assignment process. There are two types of flow of messages wherein the first type is Basic Channel Assignment Process (BCAP) (30) and the second type is Handover CA Process (40). BCAP (30) is a fundamental message flow for channel assignment process of a node pair. The first node (50) is the gateway node (91 ) or the node closest to the gateway node (91 ). The second node (70) is the subsequent node of the first node (50) The first set of the node pair includes a gateway node (91 ) and a node intermediate to the gateway node (91 ). First node (50) initiates the message flow by requesting one or more available channels information from the second node (70). The second node (70) responds with the channel information. The first node (50) performs channel evaluation and selects an applicable channel. Upon channel selection, the first node (50) sends a 'set channel' command to the second node (70) and the node pair configures the backhaul interfaces to selected channel. The node pair connects and resumes communication. Once backhaul interfaces of both the first node (50) and the second node (70) are communicating, the second node (70) sends an acknowledgement to GW to indicate the end of BCAP (30). Upon completing BCAP (30) on the first set of the first node (50) and the second node (70), the process is repeated for one or more interface of the first set of the nodes and/or repeated by one or more subsequent pair of nodes. Before the BCAP (30) is repeated by subsequent pair of nodes, the GW node assigns BCAP (30) to a subsequent node by sending a Handover CA Process (40) command.

Figure 5 illustrates an example of performing channel selection for a channel assignment process. The wireless link between a first and a second node (70) is shown in dotted line. In this particular example, the first node (50) is labeled as (h) and it is the intermediate node of the gateway node (91 ) and the second node (70) is labeled as (h+1 ) and it is the node subsequent to the first node (50). All the nodes that fall within the circle (80) are the detected active nodes and they are interferers. Active nodes can be the nodes on the same network or nodes from other networks.

In this particular example, table is used as a means of arranging data. The first column of the table indicates channel numbers. The second and the third column indicate the number of active nodes residing in the channels for both the first and the second node (70). The total number of detected active nodes is computed by adding the value of second and third column of the table. In channel 1 , there is one interferer node in the common interference zone (90). Nodes that fall within the common interference zone (90) are subtracted from the total number of detected active nodes. The total number of detected active nodes is calculated using equation (1 ). h+l

-N, Common,i ' ; / e ChannelSet

(1 ) wherein

N Total active interfaces in channel /^';

channel number;

h Number of hop from gateway (GW);

m Total number of active channel / observe by node k;

N, Common, i Number of common active channel /^'to node h & h+1 . The least interfered channel is selected based on values on the fourth column. Equation (2) computes an option of one or more channel with the least number of interferers. ch_options = min( V.) ₍₂₎ wherein

ch

options, j _ _{set 0}† _cnanne| option with minimum number of interferers.

In this example, two possible least interfering channels are identified wherein they contain the least number of active nodes. The channel 1 and channel 3 have a total of 4 interferers each. A wireless link is affected by interferers from both uplink and downlink direction with uneven interferer distribution. In this example, the uplink direction node is node h+1 wherein the downlink direction node is node h. For channel 1 , the uplink node, h+1 has 1 interferer wherein the downlink node, h has 4 interferers.

Channel 3 has equal number of interferers for uplink node, h+1 and the downlink node h. Equation (3) computes the number of difference of interferers between the uplink and downlink node. In this example, the number of difference of the interferers for channel 1 is 3 and 0 for channel 3. Equation (4) computes the one applicable channel which has the minimum difference in term of interferers. This ensures even distribution of interferers for both uplink and downlink direction. Therefore channel 3 is selected as it is the least interfered channel with the most even interferers' distribution.

wherein

Δ = Difference of number of active channel detected.

Selected = j )

(4) g

Figure 6 illustrates a method of selecting an applicable channel for a channel assignment process in a wireless network, the method includes the steps of: a) computing a number of operating nodes in at least one channel for at least one first node (50) and at least one second node (70); and

b) selecting at least one least occupied channel from the at least one channel by considering interference characteristics of the at least one first node (50) and the at least one second node (70);

wherein the at least one least occupied channel has the least number of operating nodes;

If there is more than one option of least occupied channels, the following steps are executed:

a) computing a difference of number of operating nodes for the at least one least occupied channel between the at least one first node (50) and the at least one second node (70); and

b) selecting an applicable channel with the minimum number of difference of number of operating nodes;

wherein the selected channel is used for communication between at least one interface (10) of at the least one first node (50) and at least one interface (20) of the at least one second node (70).

While several particularly preferred embodiments of the present invention have been described and illustrated, it should now be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are intended to embrace such changes, modifications, and areas of application that are within the spirit and scope of this invention.

Claims

1. A system for a channel assignment in a wireless network, the system includes: a) at least one interface (10) of at least one first node (50) constructing a means of arranging and perform a channel selection; wherein the means of arranging data includes one or more available channels information;

wherein the at least one first node (50) is a gateway node (91 ) or the node which is located nearest to the gateway node (91 ); and b) at least one interface (20) of at least one second node (70) in communication with the at least one interface (10) of the at least one first node (50) and sends one or more available channels information to the at least one interface (20) of the at least one first node (50); wherein the at least one interface (10) of at the least one first node (50) and the at least one interface (20) of the at least one second node (70) are capable of initiating a channel assignment process and identifying one or more available channels;

wherein the at least one interface (10) of the at least one first node (50) and the at least one interface (20) of the at least one second node (70) switches to the channel selected by the at least one interface (10) of at least one first node (50) and resume communication.

2. A method for channel assignment in a wireless network, the method includes the steps of: a) initiating a process wherein a default channel is used for communication; b) initiating a channel assignment process between at least one interface (10) of at least one first node (50) and at least one interface (20) of at least one second node (70);

c) identifying one or more available channels by the at least one interface ( 0) of the at least one first node (50) and the at least one interface (20) of the at least one second node (70);

d) sending one or more available channels information from the at least one interface (20) of the at least one second node (70) to the at least one interface (10) of the at least one first node (50);

e) constructing a means of arranging data including one or more available channels information by the at least one interface (10) of the at least one first node (50); f) selecting an applicable channel wherein the channel is selected by the at least one interface (10) of the at least one first node (50);

h) switching of the at least one interface (10) of the at least one first node (50) and the at least one interface (20) of the at least one second node (70) to the selected channel; and

i) connecting the at least one interface (10) of the at least one first node (50) and the at least one interface (20) of the at least one second node (70) to resume communication.

3. The method as claimed in claim 2 further includes the steps of checking if there are one or more subsequent interfaces of the at least one first node (50) and/or the at least one second node (70) that requires configuration; wherein the process comes to an end if there are no subsequent interfaces to be configured.

4. A method of selecting an applicable channel for a channel assignment process in a wireless network as claimed in claim 2, wherein the method includes the steps of: a) computing a number of operating nodes in at least one channel for at least one first node (50) and at least one second node (70); and

b) selecting at least one least occupied channel from the at least one channel by considering interference characteristics of the at least one first node (50) and the at least one second node (70); wherein the at least one least occupied channel has the least number of operating nodes;

5. The method as claimed in claim 4 further includes the steps of: a) computing a difference of number of operating nodes for the at least one least occupied channel between the at least one first node (50) and the at least one second node (70); and

b) selecting an applicable channel with the minimum number of difference of number of operating nodes; wherein the selected channel is used for communication between at least one interface (10) of at the least one first node (50) and at least one interface (20) of the at least one second node (70).