Patent Application
20070298808
A disclosed example embodiment of this invention provides for scheduling transmissions in a first direction between a hub base station and a subscriber station such as customer premises equipment using one scheduler associated with the hub base station. Communications in a second, opposite direction between the hub base station and the subscriber station is scheduled by another scheduler associated with the subscriber station. Using two different schedulers for the two different directions of communication reduces communication delays, at least in part, because it eliminates any requirement for handshaking between the subscriber station and the hub base station as was used in arrangements where the hub base station scheduler was responsible for scheduling all communications in both directions.
The example embodiment represents a significant departure from previous communication arrangements such as those used for WiMax communications, for example, where a hub base station scheduler was responsible for scheduling all communications in both directions between the hub base station and remotely located subscriber stations or customer premises equipment. This example utilizes one scheduler for controlling communications in one direction while utilizing another scheduler for controlling communications in a second, opposite direction.
A plurality of subscriber stations are within a communication range of the hub BTS 22. The illustration includes example subscriber stations 24 and 26. In this example, the subscriber stations 24 and 26 comprise customer premises equipment devices (CPEs) that are useful with WiMax communications. The CPEs 24 and 26 are located remotely from each other and the hub BTS 22.
The hub BTS 22 includes a controller portion 30 that controls communications between the hub BTS 22 and a communication network 32 in a known manner. The BTS controller 30 also includes a scheduler that uses a known scheduling algorithm in one example.
The scheduler of the BTS controller 30 in this example schedules all communications in a first direction between the hub BTS 22 and any of the CPEs with which the hub BTS 22 communicates.
Each CPE in the illustrated example has its own scheduler portion associated with the CPE. In this example, the CPE 24 has an associated base station portion 34 that includes a base station scheduler that uses a known scheduling algorithm. The CPE 26 has an associated base station 36 that includes its own scheduler. In the illustrated example, the base station portion 34 of the CPE 24 is integrated with the CPE components as schematically shown. In the case of the CPE 26, the base station 36 comprises separate components that are appropriately linked with the CPE 26 and located within close proximity to or the vicinity of the CPE 26. Given this description, those skilled in the art will realize how to arrange components to meet the needs of their particular situation.
The schedulers at each of the CPEs schedule all communications in a second direction that is opposite from the first direction between the hub BTS 22 and the corresponding CPE. For example, the scheduler associated with the base station 34 at the CPE 24 schedules all communications in the second direction between the hub BTS 22 and the CPE 24. Similarly, the scheduler associated with the base station 36 of the CPE 26 schedules all communications in the second direction between the hub BTS 22 and the CPE 26.
In the illustrated example, the hub BTS 22 includes subscriber station capabilities in a subscriber station module 40 that is configured to receive communications transmitted by the base stations associated with the CPEs. In this example, the communications from the CPEs 24 and 26 to the hub BTS 22 may be regarded as uplink communications between the CPEs and the hub BTS 22. Because a base station is used for such communications in this example, communications from the base stations 34 or 36 to the hub BTS 22 and more particularly, the subscriber station module 40 can also be considered “downlink” communications because they technically are occurring between a base station and a subscriber station module.
In this example, the first direction communications that are scheduled by the scheduler of the hub BTS 22 are those communications occurring in the direction from the hub BTS 22 to the CPEs 24 or 26. Accordingly, the CPE 24 and the CPE 26 each include receiver portions for receiving such communications. The second direction of communication in this example is from the CPEs 24 or 26 to the hub BTS 22. More particularly, in the illustrated example, the commutations in the second direction are transmitted by the base stations 34 or 36 associated with the CPEs 24 and 26, respectively, to the hub BTS 22.
In the illustration, the CPE 24 and the base station 34 share an antenna 42 for receiving communications in the first direction and transmitting communications in the second direction. The CPE 26 has a dedicated antenna 44 for receiving communications in the first direction while the base station 36 has a dedicated antenna 46 for transmitting communications in the second direction. Given this description, those skilled in the art will be able to arrange components to meet the needs of their particular situation.
Using different schedulers at the different locations allows for removing any need for handshaking to achieve the “uplink” capacity needed for each CPE. Instead, with the disclosed example, each end point can dynamically schedule unsolicited grant service (UGS) and non-UGS traffic without the traffic waste associated with configurations where a hub base station scheduler was responsible for scheduling communications in both directions. For example, if a UGS service has nothing to send, the scheduler can fill an airframe with non-UGS data. Conversely, whenever there is UTS data to send by a user, that data can be immediately sent on the current airframe, which minimizes latency. The base station schedulers on each end of the link (e.g., at the hub BTS and the subscriber station) eliminates protocol handshaking that was otherwise needed for achieving more bandwidth. The latency on each link is in this example, approximately the duration of an airframe plus processing time such as one or two milliseconds. If a typical airframe size of five milliseconds were used, the latency is now on the order of five or six milliseconds, which greatly expands the capability of the example communication system compared to the prior arrangements already described.
In one example, the frequency configuration includes Time Division Duplexing with nearly all of the airframe allocated in the CPE to hub BTS direction (e.g., the second direction). In one example, 90% or 95% of the airframe allocation is for the second direction. In one example, the minimum reserved traffic rate for WiMax communications is set below the maximum sustained traffic rate.
The end points (e.g., the hub BTS 22 and the CPEs 24 and 26, respectively) are connected using two half duplex “downlink” wireless connections scheduled by the base station at each location for the corresponding direction of communication.
Given this description, those skilled in the art will realize that various modifications to the disclosed example are possible including expanding the capabilities of the system in a variety of ways. For example, it may be useful to apply the various features of the disclosed example to communications other than WiMax communications.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.
