Enhanced SNR estimates from direct-sequence spread-spectrum demodulator statistics

2010 IEEE International Conference on Communications

2010

Next generation packet radio networks will have far greater processing capabilities than current radio systems. We propose and evaluate decoding techniques that make use of such capabilities to increase the probability of successful decoding. We propose a metric derived from statistics collected during demodulation in a binary CDMA receiver. We investigate several methods to apply the proposed metric to the demodulator's softdecision outputs prior to decoding. Our soft-decision decoding techniques are designed to mitigate the effects of interference from other signals in the frequency band. We compare the performance of our proposed metric to the log-likelihood ratio (LLR) metric, which requires that the mean signal level and noise variance are known for each bit position. Rather than attempt to estimate these parameters directly, our metric uses demodulator statistics and thus does not require pilot symbols or training sequences typically required by an LLR-based metric.

“…This function provides an estimate of the signal to noise ratio [9] for the set of symbols. A receiver capable of implementing our proposed soft-decision metric is shown in Fig.…”

Section: Soft-decision Metricsmentioning

confidence: 99%

Demodulator Statistics for Enhanced Soft-Decision Decoding in CDMA Packet Radio Systems

2010 IEEE International Conference on Communications

2010

“…The endpoints are selected such that adjacent intervals of the statistic space corresponds to a 0.5 dB difference in CENR. The endpoints can be obtained easily from simulation of a static channel or they can be determined analytically from an estimate of the signal-to-noise ratio that is derived from the PDSQ statistic [5].…”

Section: Appe Ndixmentioning

confidence: 99%

“…In this paper we employ a demodulator statistic specific to binary direct-sequence (DS) spread-spectrum modulation. The demodulator statistic is the post-detection signal quality (PDSQ) statistic, which was first introduced in [2] and subsequently employed for such applications as soft-decision decoding [3], adaptive transmission [4], and signal-to-noise ratio estimation [5]. In this paper we present and evaluate the use of the PDSQ statistic in an initial This research was supported by the Army Research Office under Grant W911NF-08-1-0442.…”

Section: Introductionmentioning

confidence: 99%

Initial power adjustment and link adaptation from direct-sequence spread-spectrum demodulator statistics

MILCOM 2009 - 2009 IEEE Military Communications Conference

2009

Statistics obtained during demodulation are used in a direct-sequence spread-spectrum packet radio network to govern the adjustment of transmitter power within the first few packets of a session. The statistics are also employed by an adaptive transmission protocol to select the modulation parameters and the rate of the error-control code for each packet. The power-adjustment protocol uses the statistics to ensure that the transmitter power level is high enough to satisfy the signal strength requirements at the receiver and low enough to prevent unnecessary interference to nearby radios. We describe a protocol for which modulation and coding parameters are adapted to achieve the most efficient com bination for the given channel conditions. We evaluate the performance of each protocol for several channels. The protocols are not given any information about the type of channel or the channel parameters, yet they are able to use the demodulator statistics to efficiently set the initial power level and adapt transmissions throughout the session.

“…For a channel without interference, it is shown in [2], that for any m the off-peak statistics in the sequence …”

Section: Combination Estimatormentioning

confidence: 99%

SNR estimation in direct-sequence spread-spectrum multiple-access systems

MILCOM 2009 - 2009 IEEE Military Communications Conference

2009

Statistics that are obtained from the demodulator are used in a direct-sequence spread-spectrum receiver to provide an estimate of the signal-to-noise ratio. We evaluate the applicability to spread-spectrum multiple-access systems of an SNR estimator that was proposed previously for SNR estimation in systems for which the only disturbance is thermal noise. The proposed estimate does not require the use of pilot symbols or additional overhead and it is obtained prior to packet decoding. The estimator does not require knowledge of the phase, amplitude, or timing of the interference signals.