David Paranchych

A method for outer loop rate control in high data rate wireless networks

A method is proposed for the control of data rate selection in mobile terminals complying with the IS-856 high data rate wireless standard. The technique involves adjusting a set of signal-to-interference-plus-noise ratio thresholds, equal in number to the number of available data rates, according to the pattern of received frame errors. The algorithm allows the mobile terminal to adapt its data rate decisions to the channel conditions, and allows fast convergence to the overall target packet error rate, an assurance of equal packet error rate for each of the different data rates, and high throughput. The proposed algorithm is practical for implementation at the mobile terminals since it works simply based on an outer loop rate control mechanism and it does not require any lookup tables or prediction of channel conditions.

On the evolution of handoff management and network architecture in WiMAX

Mobility management is an essential element of wireless communications. It is the key to enabling always-on wireless connectivity to mobile users. With the advance of the next generation broadband wireless technologies and different network architecture evolution options, the capability to achieve fast and seamless handoff is a critical factor in evaluating the success of a new technology and the efficiency of the network architecture. This paper addresses the possible handoff solutions to new broadband wireless technologies such as WiMAX under different network architectures. The key handoff issues, challenges and architectural options faced in designing the WiMAX networks are discussed

Performance improvement of the HDR system due to hybrid ARQ

One of the main improvements that the 1xEV-DO (IS-856) standard adds to the original HDR proposal is the hybrid automatic repeat request (H-ARQ) mechanism. The H-ARQ scheme combines error correction, error detection, soft packet combining and incremental redundancy. H-ARQ reduces the required forward link SINR and thereby improves overall system capacity, particularly in mobile environments. We present simulation results comparing the aggregate throughput of CDMA HDR systems with and without H-ARQ. We find that H-ARQ gives greatest gain at moderate to high mobile speeds and also at cell-edge locations, where the mean received Ec/Io is small. The addition of H-ARQ more than doubles the aggregate throughput for mobile speeds above 21 km/h.

Performance of a digital symbol synchronizer in cochannel interference and noise

The performance of a binary-quantized data-transition tracking loop symbol synchronizer operating in cochannel interference (CCI) and noise is examined for both binary phase-shift keying and quaternary phase-shift keying modulations. The CCI can be included in a previously known Markov chain model without increasing the number of states in the chain, but the cost of computing the transition probabilities increases exponentially with the number of interferers. It is shown that a first-order Markov model and simulation are in close agreement for some important applications. The effect of interferer epoch on the degradation caused by the interference is investigated and the degradations in performance caused by CCI and by Gaussian noise are compared.

Power control methods for dedicated control channels during discontinuous transmission in IS-2000 systems

We address the problem of power control for dedicated control channels (DCCHs) in IS-2000 CDMA networks during intervals of discontinuous transmission (DTX). A receiver must have the ability to distinguish between a bad traffic frame and a stoppage of transmission, if outer loop power control (OLPC) is to operate properly. We propose two new methods to facilitate the detection of a DTX interval. The first method uses measurements of the signal-to-noise ratios of the traffic channel and the power control sub-channel. The second uses explicit signaling between the transmitter and receiver. Simulations are used to assess the performance of the first method.

Performance evaluation of two transmit diversity techniques for cdma2000

This paper compares the performance of two transmit diversity schemes, orthogonal transmit diversity (OTD) and phase sweeping transmit diversity (PSTD), when utilized by the cdma2000 forward link. Each scheme is simulated for one- and two-path Rayleigh fading channels, and for a one-path Rician fading channel with different k-factors. For configurations employing a coding rate of 1/2 , it is shown that PSTD can significantly outperform OTD when the fading is Rayleigh distributed. For configurations using a coding rate of 1/3, the two methods provide similar performance under Rayleigh fading conditions. Under Rician fading conditions, OTD provides gain over PSTD for both code rates. The gain increases for higher k-factors.

On the performance of fast forward link power control in IS-2000 CDMA networks

The quality of fast forward link power control in IS-2000 CDMA systems is examined by comparing it to ideal power control, for a one-path Rayleigh channel model. Closed form expressions are derived that relate average transmitted power and average received signal-to-noise ratio for ideal power control. Simulations are used to compare the power control achievable in a Radio Configuration 3 (RC3) IS-2000 system with that of ideal power control, for the case of a slowly moving (3 kmm) mobile. In this case, IS-2000 power control requires 4 dB more power than ideal power control for 1% frame error rate (FER), and 1.3 dB for an FER of 10%. The narrow margin for improvement at large FER targets makes it unlikely that substantial capacity gain can be achieved from improved power control in networks carrying mostly data traffic, since FER targets are likely to be higher for data than for voice.

Evaluation of performance improvement of IS-2000-A in comparison to IS-2000

IS-2000 Release 0 is the standard for the first phase of cdma2000, a 3G wireless technology. Release 0 allows a maximum single channel rate of 153.6 kb/s. The next release, IS-2000 Release A, was introduced to improve the performance of cdma2000. A key enhancement increases the maximum single channel rate to 307.2 kb/s. We evaluate the performance benefits of this higher data rate feature. Simulations show there is no significant sector throughput increase. The increase in user throughput depends on system loading, and for highly loaded systems the gain is small. We analyze the dependency of throughput gain on the system power loading, and discuss the channel rate distribution and other characteristics of system performance. We provide recommendations to maximize the benefits of the 307.2 kb/s channel and identify configurations that will not benefit from 307.2 kb/s.

Capacity comparison of packet options in IS-2000 with various power control methods

A capacity comparison of packet options P1 and P2 in IS-2000 is presented in this paper. We first describe some power control methods applicable to the dedicated control channel (DCCH) during intervals of discontinuous transmission (DTX). Then a capacity comparison is made with various power control methods under a web browsing traffic model. The results show that, in general, P2 has a capacity advantage over PI. The results also indicate that the capacity comparison between packet options P1 and P2 is a function of the timer from active state to dormant state as well as the length of data duration.

Enhanced scheduling schemes to integrate QoS support in 1/spl times/EV-DO

The air link scheduler is an important element for the 1/spl times/EV-DO system to achieve high throughput and capacity. In this paper, we propose a set of enhanced scheduling schemes to integrate QoS support in 1/spl times/EV-DO. Our method exploits the time variance of the wireless channel, average user throughput, user priority and delay constraints. It has the flexibility to support various QoS criteria. Simulation results show that the proposed schemes can provide the 1/spl times/EV-DO system with the ability to treat the user differently based on the priority. With appropriately selected parameters, the degradation of the aggregated sector throughput is minimal due to the integration of QoS. Furthermore, the proposed schemes improve the overall system performance and capacity, especially for real time applications.