Asif D. Gandhi

Performance of 1xEV-DO third-generation wireless high-speed data systems

Wireless high-speed data systems based on 1xEV-DO have recently been deployed commercially and in field trials. In this paper, the emphasis is placed on the validation of the simulated forward link system-level performance through comparison with field data. High spectrum efficiency observed both in simulations and in the field is explained by the salient features of 1xEV-DO that make it suitable for data communications in a cellular mobile environment. These features include, among others, the long-range channel estimation and rate prediction, incremental redundancy hybrid automatic request control (ARQ), turbo coding, and scheduling that exploits multi-user diversity in a fast fading environment. The paper also addresses the reverse link performance and the practical system constraints imposed by the signaling overhead necessary to support high throughput on the forward link.

Forward and reverse link capacity for 1xEV-DO: third generation wireless high-speed data systems

This paper presents the performance results of a 1xEV-DO system. With different fading channels, data rate control lengths and overhead channel power levels, the system performance will vary. While optimizing the forward-link throughput becomes critical for asymmetric traffic demand, it is important to ensure that the reverse-link throughput is sufficient to support the data traffic ratio of 4:1 to 6:1 (forward/reverse). In this paper, the forward-link throughput is simulated. The final throughput is based on field measured channels for different morphologies. On the reverse link capacity, the throughput is analyzed based on an analytical formula that considers pilot, DRC and data channels.

Evaluation of the energy efficiency metrics for wireless networks

Efforts are currently underway in standards organizations to define energy efficiency metrics for wireless networks. This effort reflects current industry interest in producing networks that are as “green” as possible. Candidate metrics examine radiated base station power normalized to area and carried traffic load, e.g., Watts/Erlang/km2 or Watts/(bits/sec)/km2. While these measures appear to be a natural way of assessing efficiency, they are in fact inappropriate for use in a wireless system. Targeting such metrics is counter to prudent system operation, as well as misleading in design. We demonstrate these facts both from a theoretical and empirical perspective, noting limits based on the physics of propagation as well as analyzing field data gathered from a large Code Division Multiple Access (CDMA) network. We also use this information to suggest requirements for methods of assessing “green-ness” that are better suited to the wireless domain.

Cost effective improvement of EV-DO user experience through contention-based carrier addition

The individual user experience or throughput during a data session is key to wireless customer satisfaction. Insight into this value is not easily obtained. For example, “sample” experiences obtained through drive tests are moderately representative at best; moreover, coarse site measurements such as total data downloaded are insufficient. As the Evolution-Data Optimized (EV-DO) standard provides contention-based access, user throughput can always be improved via carrier addition; however, the absence of specific measures, as well as a means of projecting improvements, makes targeted carrier addition difficult. Using available Alcatel-Lucent site (“service”) measurements, we demonstrate a means for assessing individual user experience and projecting its improvement upon carrier addition. These results are employed within a Code Division Multiple Access (CDMA) network to implement carrier addition for targeted sites. We assess this strategy via analysis of pre- and post-add network field data, showing that carrier addition not only improved the user experience as anticipated, but unleashed pent-up data demand.