[Show abstract][Hide abstract] ABSTRACT: With the emergence of packet-based wireless broadband systems such as 802.16e, it is evident that a comprehensive evolution of the universal mobile telecommunications system specifications is required to remain competitive. As a result, work has begun on long term evolution (LTE) of the UMTS terrestrial radio access and radio access network aimed for commercial deployment in 2010. Goals for the evolved system include support for improved system capacity and coverage, high peak data rates, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operations and seamless integration with existing systems. To reach these goals, a new design for the air interface is envisioned. This paper provides a preliminary look at the air interface for Evolved UTRA (E-UTRA) and associated key technologies required to reach its design objectives. Initial E-UTRA system performance results show a 2 to 3x improvement over a reference Rel-6 UMTS system configuration [1, 2] for both uplink and downlink.
[Show abstract][Hide abstract] ABSTRACT: Multi-user scheduling and OFDM techniques are well regarded as promising candidates to provide high data- rate and reliable transmissions in future communication systems. To optimally exploit multi-user diversity and frequency selectivity, exhaustive channel information is needed for every user - an impracticality given limited feedback bandwidth. Simple and efficient feedback schemes therefore become a crucial task in designing a next generation standard. In this paper, two near-optimal feedback schemes are proposed that achieve most of the multi-user scheduling benefit with very few feedback bits. It is also shown that the feedback schemes are robust to long feedback intervals. As expected, at higher Doppler spread, the performance gap using the proposed schemes becomes larger but still provides satisfactory performance.
[Show abstract][Hide abstract] ABSTRACT: 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
[Show abstract][Hide abstract] ABSTRACT: The IEEE 802.16e system for multicast and broadcast service (MBS) is further investigated over . It is shown that 802.16e networks can exploit advanced transmission and flexible resource allocation techniques to deliver high- performance MBS delivery within the constraints of the WiMAXRelease 1 system profile. A novel per-subcarrier SINR model for single frequency network (SFN) operation is proposed for the scenario in which cyclic shift transmit diversity (CSTD) - a form of delay diversity - is applied at the base station. The utility of CSTD for 802.16e MBS delivery in term of rate and coverage enhancement is investigated in detail based on the exponential effective-SINR mapping (EESM) for frame error rate (FER) prediction. In addition, an asymptotic effective SINR approach is developed for low- complexity approximation of the EESM FER mapping, and the proposed approximation is shown to be accurate for MBS simulation, while significantly reducing simulation effort.
[Show abstract][Hide abstract] ABSTRACT: 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
[Show abstract][Hide abstract] ABSTRACT: The impact of 'advanced' mobile receivers incorporating dual-port antenna diversity and chip-rate equalization is assessed in terms of UMTS Release-5 high speed downlink packet access (HSDPA) link and system throughput. The addition of a second antenna port to the RAKE receiver increased the link-level throughput under 3GPP RAN WG4 test conditions by 25-100%, while a chip-rate minimum mean square error (MMSE) equalizer increased throughput by approximately the same amount for the time-dispersive (Pedestrian-B) channel. Assuming ideal channel estimation, the improvement in sector throughput was between 25-90% depending on the receiver configuration. Neglecting TCP, user throughput increased 50 to 100% when either receives diversity or MMSE equalization was applied, with the throughput increase becoming 100 to 200% for the dual-port MMSE case. When TCP was included, however, user throughput improvement reduced to 20% (MMSE equalizer), 33% (dual-port RAKE) and 45% (dual-port MMSE) respectively for the same system load.
[Show abstract][Hide abstract] ABSTRACT: In 3GPP W-CDMA, high speed downlink packet access functionality is implemented using the high speed downlink shared channel (HS-DSCH) and its associated control channels. In this paper, we describe the overall structure of HS-DSCH and its control channels: the high speed shaped control channel (HS-SCCH) and the high speed uplink DPCCH (HS-DPCCH). We then present detailed link and system simulation results supporting the control channel design. In addition, a new power control method to support HS-DPCCH operation during soft-handoff is described. The proposed algorithm automatically adjusts the power ratio between the control and data channels based on propagation conditions and outperform the conventional scheme with minimum impact to the DPDCH performance.
[Show abstract][Hide abstract] ABSTRACT: 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.