Teck Hu

UMTS Release 99/4 airlink enhancement for supporting MBMS services

In this paper, we first describe the UMTS architecture for supporting MBMS. Then, we describe various airlink options for carrying multicast traffic in UMTS Release 99/4 system. One can carry it over FACH or DSCH channel. We discuss why DSCH channel is not an attractive solution. Then, we discuss how rate splitting, longer TTI and STTD techniques can be used to reduce the power requirement of delivering multicast traffic over the FACH channel for MBMS users. Another possibility is to use a combination of multicast as well as dedicated channels to serve all MBMS users. Some users who are in bad conditions are served using dedicated channels and those who are in relatively good conditions are served using a multicast channel. Last but not least, we present simulation results to give us an idea of how much power is required to support MBMS.

Evolution of UMTS toward high-speed downlink packet access

An expanded effort is under way to support the evolution of the Universal Mobile Telecommunications System (UMTS) standard to meet the rapidly developing needs associated with wireless data applications. A new, shared channel — the high-speed downlink shared channel (HS-DSCH) — provides support to packet-switched high-speed data users. A number of performance-enhancing technologies are included in the high-speed downlink packet access (HSDPA) system to ensure high peak and average packet data rates while supporting circuit-switched voice and packet data on the same carrier. Lucent Technologies took a pivotal role in specifying many of these techniques, including adaptive modulation and coding (AMC), hybrid automatic repeat request (HARQ), and fat-pipe scheduling. In this paper, we provide system-level simulations results to indicate the achievable performance and capacity with these advanced technologies. We also discuss HSDPA protocol architecture along with the uplink and downlink control channel design and performance. We conclude with a discussion of potential enhancements for the future.

Adaptive Frame Switching for UMTS UL-EDCH - Ping-Pong Avoidance

In this paper, we evaluated adaptive frame length switching algorithms for the enhanced uplink dedicated channel in UMTS. Different alternatives to achieve the frame switching are presented and discussed accompanied by results from simulated system throughput performance. Moreover, we also discussed the implementation issue associated with avoiding ping-pong effect caused by mobile movement. Dynamic system simulation was performed and it showed 10% improvement by switching between 2 ms and 10 ms TTI (frame) transport channels for EDCH with different threshold selection. The results show that the adaptive switching based on the user geometry with ping-pong avoidance has the most performance gain over fixed TTI system

LTE-Advanced heterogeneous networks: Release 10 and beyond

With the basic features necessary to support Heterogeneous Networks now being incorporated into LTE-Advanced, the next step is to look forward to future evolution of Heterogeneous Networks. While active and extensive discussions are presently progressing in the 3GPP standards community, this paper first provides a review of the current LTE-Advance capability and specification support and an overview of the likely development and trends for the future specifications. Deployments of heterogeneous networks now provides operators an important tool to address growing traffic demand beyond the planned initial network roll-out. This will eventually leads to comparison to and advancement towards coordinated multipoint transmissions and receptions as a possible evolution path from the Release 10 co-channel single point transmission and reception technique. The paper explores the possible enhancements and different evolution paths highlighting their benefits and challenges.

Adaptive frame switching for UMTS UL-EDCH

In this paper, we evaluated and proposed an adaptive frame length switching for the enhanced uplink dedicated channel in UMTS. Different alternatives to achieve the frame switching are presented and discussed accompanied by results from simulated system throughput performance. The results show improvement by switching between 2 ms and 10 ms TTI transport channels for EDCH. A fixed 10 ms or 2 ms TTI transport channel structures have advantages and limitations in different areas of the radio channel conditions, scheduling strategies, and resource management. Different strategies looking to exploit the existence of a single configurable transport channel the E-DCH to perform adaptive switching is examined and results identifying the projected performance gains of a user geometry approach are presented