Weimin Xiao

Uplink Control Channel Design for 3GPP LTE

Long term evolution (LTE) of the UMTS Terrestrial Radio Access and Radio Access Network is 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 currently being specified in the 3GPP standards body. The Uplink (UL) for LTE is based on Single Carrier Frequency Division Multiple Access. The UL control channel carries non-data associated control signaling like CQI, ACK/NACK, Scheduling request etc. To maintain the low PA power de-rating, the single carrier property of the UL has to be maintained. As such, special consideration should be given to the UL control channel design. This paper discusses in detail the LTE UL control channel design and its performance.

Uplink Power Control, Interference Coordination and Resource Allocation for 3GPP E-UTRA

Evolved UTRA and UTRAN is being standardized in 3GPP standard group as a long term evolution of the 3GPP radio-access technology. The goal is to achieve 2-4 times the spectral efficiency and user throughput and much smaller latency compared to HSDPA/HSUPA. Single carrier FDMA (e.g. DFT-SOFDM) is the multiple access technique of choice for uplink transmission. Interference control is one of the key elements to achieve the target spectral efficiency and user cell- edge performance requirement, especially for uplink. In this paper, interference mitigation is implemented through slow fractional power control and interference coordination through UE alignment and FDM resource allocation. Simulation results show that these techniques significantly improve uplink sector and cell edge user throughput performance.

Random Access Design for UMTS Air-Interface Evolution

Comprehensive long term evolution of the Universal Mobile Telecommunications System (UMTS) specifications is currently ongoing to provide significant improvement over the current release. Important goals for the evolved system include significantly improved system capacity and coverage, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operations and seamless integration with existing systems. To ensure low latency, users must be able to establish a connection to the network quickly. This paper provides a preliminary design and procedure for the random access channel used to establish a connection when the mobile is not yet time-synchronized to the network in the uplink.

Performance of 3GPP high speed downlink packet access (HSDPA)

High speed downlink packet access (HSDPA) technology was standardized for 3GPP W-CDMA release-5. HSDPA includes advanced techniques such as adaptive modulation and coding (AMC), hybrid ARQ (HARQ), and fast scheduling. HSDPA can deliver a 3/spl times/ increase in sector and a 6/spl times/ increase in user throughput for some traffic models. Additionally HSDPA can support almost a 4/spl times/ increase in the number of users compared to UMTS release-99 for the same service. With advanced receivers, HSDPA can support broadband quality service with 60 users per site. This paper provides an overview of the physical layer aspects of HSDPA and discusses the improvements in sector and user throughput (with respect to release-99 UMTS) resulting from HSDPA with joint scheduling and resource allocation.

Coexistence Analysis Involving 3GPP Long Term Evolution

As the standardization of Evolved-UTRA or LTE is ongoing in 3GPP, it is important to ensure the coexistence between two LTE systems or between LTE and legacy UMTS systems sharing the same frequency band. This paper is aimed at presenting a complete view of the status and challenges of the coexistence issue. The high-level methodology, UL power control, and ACLR modeling, etc. are discussed in detail. To ensure coexistence without tightening the RF requirements and hence increasing the cost for LTE, mitigation techniques like interference-aware resource allocation are proposed and shown to be effective by simulation results.

Overview of UMTS Air-Interface Evolution

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.

TDD design for UMTS Long-Term Evolution

Long-term evolution (LTE) will provide substantial enhancements to UMTS 3G systems including improved system capacity and coverage, low latency, reduced operating costs, multi-antenna support, flexible bandwidth operations and seamless integration with existing systems. LTE supports both frequency division duplex (FDD) and time division duplex (TDD) modes to provide deployment flexibility in accordance with operatorpsilas preference and spectrum allocation. This paper presents an overview of LTE TDD design and highlights key differences with FDD. Design challenges unique to TDD are presented together with adopted technical solutions. Finally, simulation results are provided to demonstrate typical TDD system performance with data applications.

Overview of enhanced uplink for 3GPP W-CDMA

Enhanced uplink technology is currently being considered for standardization in 3GPP W-CDMA (Release-6) with the standard scheduled for completion in the 4/sup th/ quarter of 2004. Enhanced uplink technology under consideration includes advanced techniques such as adaptive modulation and coding (AMC), hybrid ARQ (HARQ), fast rate control or fast scheduling by the node-B (base station), higher peak rates (up to 2 Mbps) and a reduced transition latency between CELL_DCH, CELL_FACH and CELL_PCH states. These techniques reduce overall delay, and increase throughput significantly compared to release-99/4/5 3GPP W-CDMA. In this paper, the physical layer aspects of enhanced uplink for 3GPP W-CDMA FDD are discussed in detail with accompanying link and system simulation results. These results show that the sector and user throughput of the enhanced uplink (EU) can be improved by more than 50% compared to release-99/4/5 3GPP W-CDMA.

Multi-User Scheduling for OFDM Downlink with Limited Feedback for Evolved UTRA

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.

Multi-antenna system design for 3GPP LTE

Standardization work is nearly complete on long term evolution (LTE) of the UMTS Terrestrial Radio Access and Radio Access Network which is 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 including state-of-art multi-antenna technology needs to be deployed. This paper provides a look at different multi-antenna schemes for LTE downlink and uplink. The paper also discusses various Node-B antenna configurations and summarizes the performance of different multi-antenna schemes under various scenarios.