Patent Application
20070206500
The present invention relates generally to transmitting control information within a communication system and in particular, to a method and apparatus for beacon transmission within a multi-hop communication system.
Multi-hop communication systems typically consist of a root node (sometimes referred to as a base station (BS)) in communication with multiple relay stations (RS) and mobile stations(MS). During operation, relay stations are utilized to increase the range of a base station, essentially decoding the base station's transmissions and scheduling/retransmitting to those mobile stations outside the base station's transmission range. In a centralized multi-hop communication system or a cellular communication system, a large radio resource is required for transmitting control message from base stations and relay stations when large number of relay stations are deployed to cover an area. More particularly, all base stations and relay stations transmit a beacon once per frame with a beacon message announcing their logical address, depth, and additional optional descriptive information (for example, if it accepts children, location coordinates, . . . , etc). Because of the large amount of potential transmission, radio resources available for data transmission are limited. Therefore, a need exists for a method and apparatus for transmitting beacons within a multi-hop communication system that minimizes radio resources used.
In order to address the above-mentioned need, a method and apparatus for broadcasting information within a multi-hop communication system is provided herein. During operation a base station will instruct relay stations to skip transmissions of their control information when control messaging by all relay stations exceeds a predetermined threshold (e.g., 50% of radio resource capacity). The base station determines the relay stations to skip by periodically ranking relay stations and skipping control message transmissions for relay stations having a lowest rank. The base station additionally keeps the record of relay stations that have been skipped to prevent skipping a particular station multiple times, which may cause service disruptions.
The present invention encompasses a method for beacon transmission. The method comprises the steps of determining resources required by beacon transmissions, determining if the resources required exceeds a threshold, and rank ordering relay stations. Relay station(s) having a low rank are instructed to cease beacon transmission.
The present invention additionally encompasses a method for beacon transmission. The method comprises the steps of determining resources required by beacon transmissions, determining if the resources required exceeds a threshold, and determining a skipping rate for relay stations. Relay stations are instructed to cease beacon transmission based on the skipping rate.
The present invention additionally encompasses an apparatus comprising logic circuitry determining resources required by beacon transmissions, determining if the resources required exceeds a threshold, rank ordering relay stations. The apparatus comprises a transmitter instructing a relay station having a low rank to cease beacon transmission.
Turning now to the drawings, wherein like numerals designate like components,
As shown, communication system 100 includes base station (root node) 101 in communication with multiple relay stations 102 and mobile stations 103 (only one relay station 102 and mobile station 103 are labeled). Base station 101 acts as a communication hub for users of wireless devices (mobile stations 103) to connect to wide-area network (WAN) 104. All mobile stations 103 preferably access WAN 104 by communicating via transmissions over an RF communication channel through base station 101. It is contemplated that network elements within communication system 100 are configured in well known manners with processors, memories, instruction sets, and the like, which function in any suitable manner to perform the function set forth herein.
As discussed, relay stations 102 are utilized to increase the range of base station 101, essentially retransmitting the base station's transmissions to those mobile stations 103 outside the base station's transmission range. Base station 101 and relay station 102 typically transmit a beacon (control information) once per frame. This is illustrated in
In order to address this issue, base station 101 will instruct relay stations 102 to periodically skip transmissions of their control information when control messaging by all relay stations 102 exceeds a predetermined threshold (e.g., a percentage of radio resource capacity). Base station 101 determines the relay stations to skip by periodically ranking relay stations 102 and skipping control messages for relay stations 102 having a lowest rank. Base station 101 additionally keeps the record of relay stations 102 that have been skipped to prevent skipping too many control messages, which may cause service disruptions.
In a first embodiment of the present invention, relay stations 102 are ranked based on a quality of service required by connected mobile stations 103. Thus, in the first embodiment of the present invention, base station 101 determines those relay stations in communication with at least one mobile station 103 having a high quality of service requirement. These relay stations 102 will then be ranked high. Similarly, those relay stations 102 currently communicating with nodes having a mid-tier quality of service will be ranked lower than relay stations 102 in communication with nodes having a high quality of service. Finally, those relay stations 102 in communication only with mobile stations 103 having a low quality of service requirement will be ranked low.
In alternate embodiments of the present invention, ranking of relay stations 102 may be based on other criteria such as statistic information. For example, relay stations that have a larger number of registered (attached) mobile stations compared to other relay stations may be ranked as high. Alternatively, a probability to relay the communication between a base station and mobile stations could be used to make a relay station rank higher, with higher probability of relaying capable relay stations being ranked higher. Additionally, a relay station that may have a higher probability to have a new registration of mobile stations could be ranked as high.
Continuing, the logic flow continues to step 407 where logic circuitry 301 determines if the lowest-ranked relay station 102 is allowed to skip a control channel broadcast (beacon broadcast). As discussed above, no relay station 102 is allowed to skip more than a predetermined number (e.g., 2) beacon broadcasts. Thus, if at step 407 it is determined that the lowest-ranked relay station 102 cannot have its beacon skipped, the relay station is removed from the list of ranked relay stations (step 409) and the logic flow returns to step 405. This allows for only relay stations allowed to skip beacon transmissions to be instructed to do so.
If, however, at step 407 it is determined that the lowest-ranked relay station 102 is allowed to skip its beacon, then the logic flow continues to step 411 where logic circuitry 301 instructs transmitter 302 to transmit a “skip beacon” message to the lowest-ranked relay station and the logic flow returns to step 401. Alternatively, a “skip beacon” message may be transmitted to more than one relay station, instructing the lowest ranked relay stations to cease beacon transmission.
While the above logic flow described ranking relay stations and skipping transmissions for relay stations having a lower rank, in an alternate embodiment of the present invention transmissions from all relay stations may be skipped without ranking. Similarly, all relay stations may be ranked the same order, and thus will all need to be skipped periodically. This is shown in the logic flow of
The logic flow begins at step 501 where logic circuitry 301 determines the radio resources required by control channel transmissions of base station 101 and relay stations 102. At step 503, logic circuitry determines if the resources required by all control channel transmissions is greater than a threshold (e.g., 50%). If at step 503 it is determined that the total resources required is less than or equal to the threshold, the logic flow returns to step 501, otherwise the logic flow continues to step 505. At step 505, logic circuitry 301 determines the skipping rate of control channel transmission from relay stations 102. For example, the step of determining the skipping rate may comprise the step of determining a percentage of beacon transmissions each node will need to skip to bring the resources required by beacon transmissions below the threshold. At step 505, logic circuitry 301 will determine this percentage.
The logic flow continuous to step 507 where logic circuitry 301 accesses storage 304 to determine the relay stations whose turn it is to skip a control channel broadcast now based on the skipping rate and previous beacon skipped information. For example, if there are four relay stations broadcasting control information, to reduce control channel transmissions by 25%, one relay station will need to be skipped per frame. Logic circuitry 301 instructs transmitter 302 to transmit a “skip beacon” message to the relay stations whose turn is to skip (step 509) and the flow returns to step 501.
While the invention has been particularly shown and described with reference to a particular embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. For example, if a base station determines the ranking among the active relay stations as equal, then the base station may skip transmitting control message transmission from relay stations equally among the similarly-ranked relay stations. It is intended that such changes come within the scope of the following claims.
