transmission and reception schemes with the optimal power and rate allocation . with the sum-power constraint is Ergodic channel capacity region defined as the instantaneous capacity region averaged over all the fading states . Thus, with the assumption of perfect CSIT and infinite-length Gaussian codewords, any arrival rate vectors within the ergodic capacity region are stabilizable. On the other hand, the queue backlog size eventually grows infinite for any arrival rate vectors outside the ergodic capacity region. Therefore, the network capacity region becomes equivalent to the ergodic capacity region for this case. In practical systems, the packet duration is limited to the finite time-slot duration, which results in the finite codeword length; thus, the deviation of achievable rate from the channel capacity is inevitable. This deviation from the capacity can be addressed by using the parameter that properly scales down gap the received signal-to-noise ration (SNR) in capacity equations. With imperfect CSIT or no CSIT, the network capacity region becomes completely different from the ergodic capacity region. Type of Packet Schedulers This thesis divides schedulers into three types: channel-aware, queue-aware, and queue-channel-aware schedulers. In this section, a variety of well-known schedulers are introduced for each category. Channel-Aware Scheduler Channel-aware schedulers consider CSI in performing scheduling and tend to allocate higher data rate on the user with a better channel condition. From this opportunistic transmission, higher system throughput can be achieved by the multi-user diversity effects . QSI is only considered in such a way that the allocated rate is kept no more than the current queue backlog size. Thus, the user with a larger queue backlog size is not guaranteed to be assigned a higher data, which may result in the instability of queueing system even when the arrival rate vector is within the network capacity region. Three schedulers in this category are introduced in the following subsections. Best Channel Highest Possible Rate Scheduling Under the Best Channel Highest Possible Rate (BCHPR) scheduling policy, a user with the better channel condition takes higher priority in resource allocation. Also, user is served only if some transmit power remains after clearing queue i backlogs of users with higher priorities than user When the queue backlog size is large i.
transmission and reception schemes with the optimal power and rate allocation . Ergodic channel capacity region with the sum-power constraint is defined as the instantaneous capacity region averaged over all the fading states . Thus, with the assumption of perfect CSIT and infinite-length Gaussian codewords, any arrival rate vectors within the ergodic capacity region are stabilizable. On the other hand, the queue backlog size eventually grows infinite for any arrival rate vectors outside the ergodic capacity region. Therefore, the network capacity region becomes equivalent to the ergodic capacity region for this case. In practical systems, the packet duration is limited to the finite time-slot duration, which results in the finite codeword length; thus, the deviation of achievable rate from the channel capacity is inevitable. This deviation from the capacity can be addressed by using the gap parameter that properly scales down the received signal-to-noise ration (SNR) in capacity equations. With imperfect CSIT or no CSIT, the network capacity region becomes completely different from the ergodic capacity region. Type of Packet Schedulers This thesis divides schedulers into three types: channel-aware, queue-aware, and queue-channel-aware schedulers. In this section, a variety of well-known schedulers are introduced for each category. Channel-Aware Scheduler Channel-aware schedulers consider CSI in performing scheduling and tend to allocate higher data rate on the user with a better channel condition. From this opportunistic transmission, higher system throughput can be achieved by the multi-user diversity effects . QSI is only considered in such a way that the allocated rate is kept no more than the current queue backlog size. Thus, the user with a larger queue backlog size is not guaranteed to be assigned a higher data, which may result in the instability of queueing system even when the arrival rate vector is within the network capacity region. Three schedulers in this category are introduced in the following subsections. Best Channel Highest Possible Rate Scheduling Under the Best Channel Highest Possible Rate (BCHPR) scheduling policy, a user with the better channel condition takes higher priority in resource allocation. Also, user i is served only if some transmit power remains after clearing queue backlogs of users with higher priorities than user i. When the queue backlog size is large