Raja S. Bachu

IEEE 802.16e system performance: analysis and simulations

In this paper, the performance of a prototypical IEEE 802.16e network is analyzed via link and system simulations. The exponential effective SIR mapping (EESM) is used to map the instantaneous SINR of received signals to a service-specific packet erasure rate (PER), which is in turn used to assess the downlink and uplink network and user data throughput. A variety of data traffic models are considered, including web browsing (HTTP) and full buffer sessions, operating in flat-fading and frequency-selective multipath channels such as the ITU Pedestrian-B model. The downlink network performance of the prototypical IEEE 802.16e network is compared to a 3GPP UMTS high speed downlink packet access (HSDPA) system of similar physical dimensions. System simulation results for the prototypical IEEE 802.16e network considered show-when frequency-selective scheduling is not applied-that the IEEE 802.16e downlink has similar throughput performance as HSDPA for a 70/30 TDD DL/UL frame split but approximately 40%-50% higher spectral efficiency, although control channel overhead and uplink capacity limitation remain significant open issues for further study

Incremental redundancy (IR) schemes for W-CDMA HS-DSCH

The paper compares two hybrid automatic repeat request (HARQ) schemes using incremental redundancy (IR) which have been proposed for the UMTS (W-CDMA) high speed downlink shared channel (HS-DSCH). Their relative throughput performance is reported for various channel conditions. It is shown that the two-stage rate-matching scheme has marginally worse performance compared to the alternative block interleaving scheme for certain coding rates and under some channel conditions.

Linear Interference Cancellation for Downlink Map Reception in IEEE 802.16E

Next generation wireless systems, such as the IEEE 802.16e specification, are designed to provide great flexibility in scheduling radio resources on a per frame basis. Such flexibility, coupled with the need to maintain good quality of service (QoS) for cell-edge users can, however, lead to significant control channel overhead especially when using low code rates to maintain cell edge coverage. It is shown here that in interference-limited scenarios dual antenna mobile stations (MS) equipped with interference cancellation (IC) receivers can significantly alleviate this problem. In this study, the performance of a linear MMSE IC receiver is evaluated both at the link level and at the network level. It is shown that a practical IC receiver can achieve link performance gains in the range of 2.5-14 dB over a maximal ratio combining (MRC) receiver in single interferer dominant conditions. Performance at the network level is evaluated using the well-known EESM method to model the link-level performance for OFDM systems, and the introduction of IC receivers at the MS is shown to increase control channel coverage by 10-24% at low codeword repetition factors