Bibhu Mohanty

HSUPA Scheduling Algorithms Utilizing RoT Measurements and Interference Cancellations

This paper discusses several important aspects in the HSUPA scheduling algorithms. First, it clearly demonstrates the benefit of explicitly utilizing the directly measured Rise-over- Thermal(RoT) values in term of capacity and robustness improvement. This paper also briefly presents the RoT measurement schemes designed specifically for the asynchronous systems such as WCDMA/HSUPA. If pilot and traffic interference cancellation (IC) schemes are implemented at the Node B receiver, this paper presents a scheduling algorithm that attains IC benefit in such a way that the capacity enhancement is maximized while fairness and link budget are maintained. The presented algorithm defines the effective RoT by monitoring the IC performance in real time and adjusts its grants accordingly. In addition, the user priority function used here optimizes the sum utility functions and provides multi-user diversity.

Concurrent bandwidth aggregation over wireless networks

Mobile client platforms have emerged with the ability to access and utilize multiple wireless networks concurrently. Aggregation can be performed using wireless modems on one device or cooperatively across devices within wireless proximity of each other. This paper explores various concurrent bandwidth aggregation schemes. The aggregation can be achieved on the application-layer, transport layer like MultipathTCP, or on layers below IP such as the RLC layer. These schemes are compared. In general, aggregation on the lower layer is closer to the client device and easier to adapt to the varying channel and loading conditions. However, lower layer aggregation needs more changes to wireless access stratum infrastructure. Aggregation above the IP layer is simpler to implement. A feasibility study of MultipathTCP aggregation over multiple WWANs is presented.

Performance Analysis of Dual-Carrier HSDPA

The newly standardized Dual-Carrier HSDPA offers two-carrier aggregation on the downlink. In this paper, we investigate the performance gains from the dual-carrier operations with both full buffer and bursty traffic models. With full buffer traffic, dual-carrier offers dynamic load balancing and increase in user data rate, system capacity and spectral efficiency. All the users throughout the system enjoy the data rate increase. With bursty traffic, dual-carrier provides substantial gain in user experience measured by burst rates or latency under all loading conditions. Moreover, the gain with bursty traffic is universal not only for all the users but also for a very wide range of scheduling algorithms. Our results are based on analysis and extensive simulations. Design issues are also addressed in this paper.

COBA: Concurrent Bandwidth Aggregation - A Case Study in Parallel Wireless Communications

Parallel Wireless Communications is an emerging area of research that enables mobile clients to access and utilize multiple wireless networks concurrently. This paper explores concurrent bandwidth aggregation techniques to enable parallel wireless communications on mobile devices. Concurrent aggregation can be performed using wireless modems on one device or cooperatively across devices within wireless proximity of each other.. The aggregation can be achieved on the application-layer, transport layer like MultipathTCP, or on layers below IP such as the RLC layer. These schemes are compared. In general, aggregation on the lower layer is closer to the client device and easier to adapt to the varying channel and loading conditions. However, lower layer aggregation needs more changes to wireless access stratum infrastructure. Aggregation above the IP layer is simpler to implement. A feasibility study of MultipathTCP aggregation over multiple WWANs is presented. The aggregation scheme on the RLC layer in evolved HSDPA is also presented, including protocol design and performance evaluation.

Performance Gains of Single-Frequency Dual-Cell HSDPA

In this paper, we will study the scheme of Single-Frequency Dual-Cell HSDPA (SF-DC HSDPA) which is introduced to simultaneously transmit two separate packet streams from two cells to a mobile. The inter-stream interference is suppressed by the linear-MMSE equalizer at the mobile. In the simple implementation studied in this paper, the schedulers at the two cells are independent without information exchange. Our study is based on both analysis and simulations. SF-DC HSDPA offers significantly higher data rates to users in the handover region. It also achieves dynamic load balancing in terms of resource utilizations across cells. Furthermore, all these gains can be obtained without degrading the performance of users not in handover and the legacy users. The gain from SF-DC is particularly substantial for users in heavily loaded cells surrounded by lightly loaded neighboring cells. In addition, such gain can increase with loading at a given loading ratio between the heavily loaded and lightly loaded cells. SF-DC is easy to implement with only incremental complexity to the current mobile and network equipment.

Enhanced HSDPA Mobility Performance: Quality and Robustness for Voice over HSPA Service

Legacy High Speed Downlink Shared Channel (HS-DSCH) Serving Cell Change (SCC) procedures in deployed HSPA networks (3GPP Release 5 and 6) may lead to unacceptably high call drop rates in realistic Urban Canyon conditions when Signaling Radio Bearers (SRBs) are mapped on the HS-DSCH. Mapping SRB on HS-DSCH is necessary to enable high capacity voice over HSPA (Circuit Switched Voice or VoIP over HSPA) since it eliminates the code limitation that arises when SRBs are mapped on DCH. To address the above robustness issue, Enhanced SCC (ESCC) was introduced in 3GPP Release 8. In this paper we highlight the first ever implementation of the E-SCC algorithm in a HSPA prototype system. A comprehensive evaluation of the E-SCC algorithm for voice over HSPA is performed through measurements made over a prototype network. We show that under tough urban canyon conditions, the ESCC procedure provides significant gains compared to the legacy USCC procedure in terms of call drop rates, packet drops and duration of serving cell change, thus allowing robust high quality voice service under mobility conditions. To conclude, this paper provides evidence that E-SCC algorithm implementation is feasible and when implemented, robust mobility for voice over HSPA can be achieved.

Performance of VoIP services over 3GPP WCDMA networks

We analyze the performance of voice services over 3GPP WCDMA networks for Release 99 and Release 7 deployments. We show, by using simulations, that the system capacity of Release 7 VoIP is significantly higher than the Release 99 circuit-switched voice under similar system conditions and voice quality. These results are obtained under the 3GPP simulation assumptions where uplink and downlink constraints for power, code and interference are considered. Both AMR 12.2 and 5.9 as well as different types of mobile receivers (Rake and equalizer, single and dual receive antennas) are considered. We also show that the capacity and performance can be increased significantly further by using uplink interference cancellation at the base station. The performance of best effort traffic in the presence of voice users is also analyzed.

Coverage and capacity analysis of hybrid home networks

A hybrid home network is a network consisting of hybrid devices capable of both Wi-Fi and powerline communications. We provide a comparison of coverage and capacity between hybrid, standalone Wi-Fi, and standalone powerline networks. We demonstrate that hybrid networks improve both the coverage and the capacity of a home network to simultaneously support high definition video streaming and mobile devices. The analysis is extended to show that the benefits of hybrid networks are amplified when multi-hop topologies are supported.

Circuit-Switched Voice Services Over HSPA

Circuit-Switched (CS) Voice Services over HSPA (CSoHS) was recently introduced for 3GPP WCDMA Release 7/8 systems. The benefits of this feature include improving voice and data system capacity by utilizing the enhancements offered by the shared packet transport of HSPA air interface while preserving the already widely deployed core networks. In this paper, we discuss the operation and implementation of CSoHS and analyze its performance via simulations. We show that the system capacity of CSoHS is significantly higher than Release 99 CS voice under similar system conditions and voice quality.

Dual Cell HSDPA Application Performance

Dual Cell HSDPA (DC-HSDPA), which was introduced in Release 8 of the WCDMA specifications, enables the User Equipment (UE) to receive downlink data on two adjacent carriers simultaneously. Although the user physical layer throughput is expected to double compared to a single carrier HSDPA (SC-HSDPA) system, it is not quite clear how this would translate to user experience for realistic applications in various operating scenarios, i.e. channel conditions and loading. We implemented DC- HSDPA functionality in a prototype and evaluated its performance for various applications in comparison with SC-HSDPA. Our results show that, with DC-HSDPA, realistic applications such as web browsing and video streaming see significant gains in lab as well as OTA environments compared to SC-HSDPA with or without loading due to other users. Our results also highlight the ability of DC-HSDPA UEs to improve application performance by taking advantage of uneven loading across carriers, which may result due to UEs operating on a single carrier.