Wireless communication systems, for example packet based communication systems, may provide voice telephony using Voice-over-Internet-Protocol (VoIP). Any historical demarcation between “data” and “voice” has become blurred in packet based communication systems such that the term “data” usually signifies payload information for any service, whether voice or data, such as may be provided by downloading from the Internet. Differences remain however in that voice will generally employ smaller packet sizes, for example, due to delay sensitivity than would traditional so-called data. A non-voice packet may be larger than a kilo-byte while a voice packet may be only approximately 15-50 bytes. Because the smaller packet sized utilized by voice session, a greatly increased number of voice users may be served thereby placing a burden on the control mechanisms and resources of the communication system.
Systems that employ Hybrid Automatic Repeat Request (HARQ) may make use of persistent channels for retransmissions. Persistent channels eliminate the need for mobile station to decode control channel information for each HARQ retransmission, thereby reducing control channel information for each HARQ retransmission, thereby reducing control channel overhead. To make efficient use of the resources of the communication system, however, it is necessary to reassign the persistent channel for one mobile station, once the packet is acknowledged, which requires additional overhead.
In order to assisting in providing mobile stations with resources for HARQ retransmissions with persistent assignments but without significantly increasing the overhead of the communication system, the prior art uses a sequence of super frames that generally comprise a number of super frames within each super frame comprise a number of frames. The frames within each super frame may have a resource assignment control channel portion within a control channel portion and a data channel portion. Two frames can be grouped together to form a long frame. An interlace pattern is defined as a sequence of regularly distanced long frames. For systems employing synchronous hybrid automatic repeat request (S-HARQ), the initial and subsequent retransmission typically occur in the same interlace patter.
For orthogonal frequency division multiple access (OFDMA) systems, a forward link VoIP bit map approach also applies to a reverse link. The frames have a bit map frame and a physical channel frame. The bit map frames indicate which terminals are receiving resources in the physical channels and can assign which of the physical channels to a given terminal. In one embodiment of the prior art, resources are pre-assigned to terminals and the bit map simply indicates the presence of a resource in use. Thus, each terminal in the bit map is associated with a given location in the bit map, and each location within the bitmap is associated with a unique predefined radio resource. Thus, for example, when a “1” is designated in a location within the bit map, the terminal knows that a resource is provided on the physical channel associated for that terminal. In this embodiment, typically, there is a one-to-one association between the user bit map and the physical channel, referred to as the resource bit map, such that the first position in the bit map aligns with the first physical channel in the resource bit map, the second position in the bit map aligns with the second physical channel in the resource bit map and the nth position in the bit map aligns with the nth physical channel in the resource bit map.
In another embodiment, resources are not pre-assigned to terminals, but rather, assigned to terminals with their bit locations set to “1” in a round-robin or some other pre-specified order. Each terminal is associated with a location within a bit map, and the nth assigned terminal corresponds to the nth radio resource. When a “1” is designated in the location within the bit map for a given terminal, the terminal knows that a resource is provided in the physical channel such that the terminal is the nth assigned terminal the nth physical channel is assigned to that terminal. For example, the terminal assigned to bit map position determines that a physical channel includes resources for that terminal, the terminal determines that how many other terminals have previously been assigned a physical channel and the next physical channel is assigned to that terminal. Thus, a terminal assigned to bit map position 10 detects a “1” in that location determines that 5 other terminals in bit map positions 1-9 have been assigned physical channels knows that the sixth physical channel is assigned to that terminal.
In another embodiment, the bit map is divided into two sections. The first section is for a subgroup of terminal that receives an indication of which terminals in the group are beginning new transmissions. Other subgroups are not represented in the bitmap, except through the first section of the bitmap which indicates which previously-signaled transmissions to them are ongoing. A control channel bit map can be divided into two sections where the first section contains one bit per channel and the second section contains one bit per wireless terminal for which a first HARQ transmission is intended. Only wireless terminals for which a first transmission is intended are indicated in the bit map. The nth active wireless terminal for which a transmission is intended (“1” in the second section of the bit map) is assigned the nth resource not indicated as active in the first section of the bit map. This resource is a persistent assignment, meaning the terminal does not need to decode the control channel again until its next first transmission opportunity. Thus, an assigned terminal in the user bit map gets the next available resource in the resource bit map. In an embodiment, the user bit map indicates to a user that it is to be assigned a new physical channel in the resource bit map. In response, the terminal is assigned the first available resource in the resource bit map. Accordingly, the beginning, or fore, portion of the resource bit map is used before the end, or aft, portion of the bit map. According, the aft portion of the resource bit map is not used.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
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