Donna Ghosh

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.

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.

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.

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.

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.

Repeaters and Remote Radioheads in EVDO Networks

This paper studies the different uses of repeaters and remote radioheads (fiber repeaters) in cellular networks. Traditional uses include coverage extension and eliminating points of pilot pollution (three-way handoff). In addition, we find that careful placement of repeaters can improve capacity substantially. We also find that in layouts where some sectors are much more heavily loaded than others, remote radioheads can be used to transfer load from heavily loaded to lightly loaded sectors, thereby improving network capacity. Therefore, repeaters can enhance network performance without changing either the software or the hardware of existing layouts.

On Spatial Load Balancing in wide-area wireless networks

Load Balancing is typically used in cellular wireless networks in the frequency domain to balance paging, access, and traffic load across the available bandwidth. In this paper we extend the concept of Load Balancing to the Spatial domain. We develop two approaches - Network Load Balancing and Single-Carrier MultiLink - for Spatial Load Balancing. While these techniques are applicable to both cellular wireless networks and WiFi networks we illustrate them on EV-DO (a 3G cellular data network). Both these methods apply when the device has more than one candidate server and determine the server(s) using not only the channel quality from the server to the device but also the current load on each server. The proposed techniques leverage existing cellular (EV-DO) network architecture and are fully backward compatible. Network operators can realize both a substantial increase in network capacity and deliver a notable improvement in user experience by applying these techniques. The combination of load balancing in the frequency domain (Smart Carrier Management and multi-carrier) and spatial domain improves the connectivity within a network, enabling an optimal allocation of resources under the p-fair criterion.

Distributed scheduling for wireless networks

We pose a network-wide scheduling problem for cellular wireless networks in which users are capable of being served by several schedulers on the downlink, though not jointly. We present a distributed algorithm, with limited communication across servers, that solves this problem optimally, in that it gives the network-wide proportional fair solution. An idealized version is presented first, in which all users are capable of being served by all schedulers and in which all the decision-making takes place among the schedulers alone. A practical version is also presented, in which users play a role in choosing their servers and servers decide how to allocate resources to the users that choose them. The practical version can achieve the same optimum as the idealized one and gives gains up to 60% in typical network deployments. This version can be implemented on any wireless technology to achieve optimal network scheduling. We have focused particularly on LTE, HSPA and 1xEV-DO and the first commercial deployment will soon occur on the 1xEV-DO system, based on the 3GPP2 standard, under the rubric of ‘Smart Networks.’

Uplink Resource Allocation for Multicarrier CDMA Networks with Interference Cancellation

We formulate the uplink resource allocation problem in CDMA wireless networks with interference cancellation in the load domain, which is an exact linearization of the single- cell single-carrier loading and transmit power feasibility constraints. We present a simple cooperative distributed algorithm that solves the single-cell allocation problem when posed in a utility-maximizing framework, and relate it to the uplink allocation design of the cdma2000 1xEV-DO Rev A system. We extend to the multicarrier uplink allocation problem and discuss conditions under which allocation convexity is preserved. We provide guidelines on how the results generalize to the multicarrier multi- cell network allocation problem, and how full resource allocation expressibility has been incorporated into the 1timesEV-DO Rev B uplink design. Though 1timesEV-DO examples are used throughout, the analytic approach of this paper applies to any CDMA uplink, including WCDMA.

Imbalance compensation in heterogeneous DO networks

This paper studies the effects of heterogeneity in DO networks and proposes measures for reducing or removing them. In particular, two types of imbalance, i.e., f-Imbalance and OH-Imbalance are identified and methods for compensating them, i.e., RL padding and AT overhead (OH) channel boost, are proposed. The effectiveness of the proposed methods is demonstrated through both, developing an analytic model and conducting comprehensive simulations. The main conclusion of the paper is that through a combination of methods such as partial RL padding of weaker cells and OH channel boost of ATs, it is possible to compensate for the potentially severe imbalance conditions that heterogeneity brings about to DO networks.