Patent Application
20110176516
In most communication systems bandwidth is a limited resource that is allocated for communications between endpoints. Bandwidth in wireless communication systems is typically limited by the amount of licensed frequencies and interference in a particular geographic area. In structured wireless communication systems the network typically controls the allocation of bandwidth for transmissions from the base station to the wireless stations (i.e., downlink transmissions) and transmissions from the wireless stations to the base stations (i.e., uplink transmissions). The particular manner in which bandwidth is allocated for uplink and downlink transmissions is typically defined by international standards bodies, and network operators typically do not deviate from the allocation techniques defines by international standards bodies.
Exemplary embodiments of the present invention provide systems and methods for bandwidth allocation. As will be described in more detail below, exemplary embodiments of the present invention associate one or more ranging codes to each of a plurality of service flow types, and a wireless station can use one of the plurality of received codes to request bandwidth.
An exemplary method involves a base station transmitting to a wireless station an identification of a plurality of codes and an associated service flow type for each of the plurality of codes. The base station receives a bandwidth request message from the wireless station, the bandwidth request message being one of the plurality of codes. The base station then transmits a bandwidth allocation message to the wireless station in order to allocate bandwidth based on a service flow type associated with the received code.
The allocated bandwidth can be a minimum reserved traffic rate (MRTR) for the service flow type associated with the received code. The wireless station uses the allocated bandwidth to send a data burst. If additional bandwidth is required, the data burst can include a request for additional bandwidth. The request for additional bandwidth can be included in a bandwidth request header portion of the data burst.
More than one of the plurality of codes can be associated with each of the plurality of service flow types. The plurality of service flow types can include real-time polling services (rtPS), extended real-time polling services (ertPS) and non-real-time polling services (nrtPS).
The plurality of codes can be orthogonal codes, such as code division multiple access (CDMA) codes. The allocation and data transmissions between the base station and wireless station can be performed using orthogonal frequency division multiple access (OFDMA).
The identification of the plurality of codes and the identification of the associated service flow types can be transmitted in an uplink channel descriptor (UCD).
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
In the frame of
The base station periodically identifies a location within the frame for wireless stations to use for bandwidth request and paging information in a compressed UL-MAP (step 210). This is the starting point for the uplink bandwidth request process. A wireless station randomly selects one of the CDMA ranging codes and transmits the selected code to the base station (step 215). This is a contention based process and the transmission from the wireless station to the base station can collide with other bandwidth requests due to the selection of the same CDMA code by other wireless stations. It will be recognized that only the code itself is sent, but there is no identification of the wireless station that sent the code.
Approximately 4 frames later the base station transmits a CDMA UL allocation information element (IE) in the compressed UL-MAP requesting that the wireless station identify the amount of bandwidth required (step 220). Because the base station is not aware of the identification of the wireless station that sent the ranging code, this transmission is a broadcast transmission. The wireless station responds with the amount of requested bandwidth in a bandwidth request header message in the uplink data channel (step 225). The base station then responds with an uplink channel allocation information element (IE) in the compressed UL-MAP approximately 3 frames later (step 230).
There is an inherent delay (Z) between the receipt of the bandwidth request header and the transmission of the UL Allocation IE, the delay being dependent upon the particular base station scheduler design and the system loading. The amount of bandwidth that is actually allocated depends not only on the amount of bandwidth requested but also on the amount of physical resources available (i.e., the number of subcarriers), interference and allocated power. The mobile station can then begin to use the allocated bandwidth by transmitting an uplink data burst in one of the uplink data channels (step 235). The entire bandwidth allocation process, starting from the transmission of the information elements (IEs) for the CDMA bandwidth request and ranging until the actual allocation is at least 8 frames (i.e., 40 ms), not accounting for any delays associated with the base station scheduler (i.e., delay Z).
The base station periodically identifies a location within a frame for transmission of bandwidth requests and ranging information using the compressed UL-MAP (step 310). Whenever a wireless station desires bandwidth the station requests bandwidth by transmitting one of the CDMA codes for the service flow desired by the wireless station (step 315). The wireless station transmits the code itself, but not an identification of the wireless station. The base station responds by providing the uplink allocation information element (IE) for the corresponding service flow in the compressed UL-MAP (step 320). Because the base station is not aware of the identity of the wireless station that sent the code, this message is a broadcast message. The amount of bandwidth that is allocated is a minimum reserved traffic rate (MRTR) for the particular service flow. The wireless station can then begin to use the allocated bandwidth by transmitting an uplink data burst (step 325). If the wireless station desires bandwidth beyond the minimum reserved traffic rate MRTR for the particular service flow, the wireless station can request additional bandwidth using a bandwidth request header in the initial uplink data burst.
As can be seen by comparing the call flows of
The bandwidth allocation procedure of the present invention introduces the concept of service flow specific bandwidth ranging codes, which is not currently specified in the 802.16 WiMAX standard. Thus, the convention Uplink Channel Descriptor (UCD) Type/Length/Value (TLV) can be used to identify assignment of codes to specific service flow types. The UCD TLV is specified in section 11.3 in 802.16, Rev2/D1 Part 16: Air Interface for Broadband Wireless Access Systems, the entire disclosure of which is herein expressly incorporated by reference. Additionally, the Uplink Allocation Start information element (IE) should include proper syntax to specify the dedicated ranging code, ranging symbol and ranging subchannel. These pieces of information are currently carried in the CDMA Allocation IE, and not the Uplink Allocation Start IE.
Although the present invention has been described in connection with one base station and one wireless station, the present invention can be used by more than one wireless station supported by any particular base station and by any number of base stations in a network. Additionally, although the present invention has been described as using particular messages, the present invention can be employed with different messages. Finally, the specific service flows described above are merely exemplary and the present invention can employ any type of service flows.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
