Christopher Gerard Lott

CDMA2000 1/spl times/EV-DO revision a: a physical layer and MAC layer overview

This article presents key enhancements to CDMA2000 1/spl times/EV-DO systems embodied in 1/spl times/EV-DO Revision A. These enhancements provide significant gains in spectral efficiency and substantial improvements in QoS support relative to 1/spl times/EV-DO Revision 0. In particular, 1/spl times/EV-DO Revision A approximately doubles the uplink spectral efficiency and doubles the number of terminals with delay-sensitive applications that can be simultaneously supported on the system. It provides substantial reduction in latencies (approximately 50 percent) during both connection setup and the connected state. It offers comprehensive network control over terminal and application performance to enable the desired trade-offs between capacity and latency/ fairness, thereby providing full QoS support and enhanced user experience. It also provides coverage improvement (approximately 1.5 dB) relative to 1/spl times/EV-DO Revision 0. This enables operators to offer services such as VoIP, video telephony, mobile network gaming, push-to-talk, Web browsing, file transfer, and video on demand to a larger number of simultaneous users. The 1/spl times/EV-DO Revision A network can provide downlink sector capacity of 1500 kb/s and uplink capacity of 500 kb/s (two-way receive diversity) or 1200 kb/s (four-way receive diversity) with 16 active users per sector, using just 1.25 MHz of the spectrum.

Hybrid ARQ: Theory, State of the Art and Future Directions

Hybrid ARQ transmission schemes combine the conventional ARQ with forward error correction. Incremental redundancy hybrid ARQ schemes adapt their error correcting code redundancy to varying channel gains, and thus achieve better throughput performance than ordinary ARQ, particularly over wireless channels with fluctuating channel conditions. Consequently, the scheme has been adopted by a number of standards for mobile phone networks. We provide a brief survey of theory and state of the art of hybrid ARQ, and present some possible future directions keeping in mind practical considerations.

Stochastic routing in ad-hoc networks

We investigate a network routing problem where a probabilistic local broadcast transmission model is used to determine routing. We discuss this models key features, and note that the local broadcast transmission model can be viewed as soft handoff for an ad-hoc network. We present results showing that an index policy is optimal for the routing problem. We extend the network model to allow for control of transmission type, and prove that the index nature of the optimal routing policy remains unchanged. We present three distributed algorithms which compute an optimal routing policy, discuss their convergence properties, and demonstrate their performance through simulation.

Evolution of cdma2000 cellular networks: multicarrier EV-DO

The evolution of cdma2000 1xEV-DO systems to multicarrier EV-DO (supported by 1xEV-DO Revision B) is discussed in this article. Multicarrier EV-DO offers a backward-compatible upgrade to leverage existing 1xEV-DO networks and terminals. It allows a software upgrade to multicarrier EV-DO using 1xEV-DO Revision A base station hardware. Multicarrier operation achieves higher efficiencies relative to single-carrier by exploiting channel frequency selectivity, improved transmit efficiencies on the reverse link, and adaptive load balancing across carriers. Multicarrier EV-DO enables very high-speed download, high-resolution video telephony, and improved user experience with concurrent applications. The sources of higher efficiency are discussed in detail in this article. It also enables hybrid frequency reuse deployment scenarios that enable spectrally efficient operation and significant improvement in edge coverage performance with hardware-efficient implementations. The evolved wider bandwidth systems (up to 20 MHz) based on multicarrier EV-DO offer operators a cost-effective solution that competes favorably with other technologies.

VoIP over cdma2000 1xEV-DO revision A

In this article we analyze performance of VoIP services over 1xEVDO-Revision A (DO-Rev A) networks and show that high-quality VoIP with unconstrained mobility and high capacity can be achieved. Together with quality of service (QoS) requirements, we emphasize practical issues such as mobility, degradation of feedback-channel quality, and packet overheads. Novel techniques are presented for voice processing such as smart blanking and adaptive dejitter playback buffer with time warping. These techniques help to meet QoS constraints to achieve a circuit-like voice quality while improving overall capacity. Detailed end-to-end simulations are presented and system capacity is analyzed under the QoS and system stability constraints. We claim that DO-Rev A can provide VoIP capacity comparable to circuit-switched cellular CDMA technologies (e.g., IS-2000) and simultaneously carry significant amount of other types of traffic such as non-delay sensitive applications and downlink multicast.

On the reverse link performance of cdma2000 1/spl times/EV DO revision A system

cdma2000 1/spl times/EV-DO release 0 (DO ReL. 0), also known as IS-856, is a third generation (3G) wireless solution to providing wide-area high-speed mobile Internet access. cdma2000 1/spl times/EV-DO revision A (DO Rev. A) system provides enhancements to DO Rel. 0, such as higher spectral efficiency and advanced quality-of-service (QoS) support. In this paper we evaluate the reverse link performance of DO Rev. A system from a physical layer perspective. Specifically, we obtain DO Rev. A reverse link capacity via analysis as well as system simulations with complete modeling of physical- and MAC-layer dynamics. We show that DO Rev. A achieves significant capacity gain over DO Rel 0 in supporting delay-sensitive applications and provides flexible tradeoff in delay, capacity and physical-layer error-rate performance based on QoS requirement. Under moderate sector loading, DO Rev A achieves a reverse link sector capacity on the order of 600-700 kbps with two receiving antennas, i.e. a two-to-three fold improvement over DO Rel 0, while using the same 1.25 MHz of spectrum. Furthermore, sector throughput on the order of 1.2 Mbps is achievable with four receiving antennas, in the form of spatial array or pairs of cross-polarized (X-pol) antennas.

3GPP LTE Downlink System Performance

In this paper we quantify 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) Release 8 downlink system performance for a macro cell hexagonal grid scenario. The system performance is analyzed for a closed loop Single User Multi-Input Multi Output (SU-MIMO) mode and compared with Single Input Multiple Output (SIMO) and Multi-User (MU) MIMO modes, for a full buffer scenario and static users. In addition to the full buffer scenario, traffic models are considered for SIMO mode to evaluate impact of partial loading and handover. Voice over Internet Protocol (VoIP) system performance is quantified for static users. Mobility simulations are performed for Video Telephony (VT) users and compared to the static case.

Reverse traffic channel MAC design of cdma2000 1xEV-DO revision A system

cdma2000 1xEV-DO (DO), also known as IS-856, is a third generation (3G) wireless solution providing high-speed mobile Internet access. cdma2000 1xEV-DO revision A (DO-RevA) system provides further enhancements to DO, such as higher system capacity and advanced quality-of-service (QoS) support In this paper we motivate and describe the design of the reverse link traffic channel MAC (RTCMAC) of DO-RevA system, which uses a novel combination of centralized specification of flow behavior together with autonomous mobile packet allocation subject only to resource congestion control. We demonstrate that RTCMAC achieves full resource allocation flexibility through an efficient robust design, well suited to the CDMA reverse link.

On the fairness and stability of the reverse-link MAC layer in cdma2000 1/spl times/EV-DO

We investigate the fairness of two reverse-link MAC algorithms in cdma2000 1/spl times/EV-DO high rate packet data systems. Following the framework proposed by Kelly for Internet congestion-control, we formulate a utility maximization problem and provide a simple sufficient condition for both algorithms to converge to the solution of this problem. Furthermore, we identify that the solution of this problem corresponds to the equal throughput fairness criteria, i.e., all the access terminals have equivalent throughput at the equilibrium.

Uplink-Downlink Imbalance in Wireless Cellular Networks

Uplink-downlink imbalance is a characteristic of all wireless networks which greatly impacts system performance, and must be accounted for in system design and simulation. However this property seems to have received sparse attention in literature. This paper describes imbalance, its potential sources, audits impact on traffic and overhead channel performance, soft handoff adaptive server selection, and sector load control schemes. This paper defines imbalance metrics, a model for simulating antenna imbalance, and presents simulation study of system robustness to link imbalance using cdma2000 1xEV-DO as an example.