Conference Paper

Modified pulse repetition coding boosting energy detector performance in low data rate systems

Commun. Technol. Lab., Swiss Fed. Inst. of Technol., Zurich, Switzerland
DOI: 10.1109/ICU.2005.1570040 Conference: Ultra-Wideband, 2005. ICU 2005. 2005 IEEE International Conference on
Source: IEEE Xplore


We consider ultra-wideband impulse radio (UWB-IR) low data rate (LDR) applications where a more complex cluster head (CH) communicates with many basic sensors nodes (SN). At receiver side, noncoherent energy detectors (ED) operating at low sampling clock, i.e., below 300 kHz, are focused. Drawback is that EDs suffer from significant performance losses with respect to coherent receivers. Pulse repetition coding (PRC) is a known solution to increase receiver performance at the expense of more transmit power. But in LDR systems known PRC is very inefficient due to the low receiver sampling clock. Boosting transmit power is not possible due to Federal Communications Commission's (FCC) power constraints. Hence, we present a modified PRC scheme solving this problem. Modified repetition coded binary pulse position modulation (MPRC-BPPM) fully exploits FCC power constraints and for EDs of fixed integration duration is optimal with respect to bit error rate (BER). Furthermore, MPRC-BPPM combined with ED outperforms SRAKE receivers at the expense of more transmit power and makes ED's performance robust against strong channel delay spread variations.

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    • "However, noncoherent receivers offer simpler architecture and lower power compared to coherent receivers [1]. Therefore, non-coherent architectures are attractive solutions for low cost, low complexity, and very low power applications [3] [4] [5] [6]. "
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    ABSTRACT: Non-coherent UWB receivers are often implemented using energy detection architectures which are very sensitive to noise in the channel and interference. Therefore, the receiver bandwidth plays an important role since the total noise and interference energy is proportional to this bandwidth. This work provides analytical expressions to find the optimal receiver bandwidth and quantifying the effect on the bit-error-rate (BER) due to channel noise and adjacent-channel interference (ACI). A reduction in receiver bandwidth beyond the optimal point is shown to have minimal impact on BER performance when ACI is negligible.
    2011 IEEE Wireless Communications and Networking Conference, WCNC 2011, Proceedings, Cancun, Mexico, 28-31 March, 2011; 01/2011
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    • "This is possible as the specific ISI structure allows the receiver to collect the entire signal energy while integrating over a shorter duration. This gain leads to advantages of UWB TR over differential phase shift keying (DPSK) systems in presence of ISI and the FCC peak power constraint [5]. The paper is organized as follows. "
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    ABSTRACT: We consider a wireless body area network (WBAN) with an average per link throughput of about 500 kbps based on an ultra wideband (UWB) transmitted reference (TR) scheme. For a long battery autonomy a low duly cycle operation of the nodes and thus a high peak data rate is a promising concept. Due to a moderate path loss, a peak data rate in excess of 50 Mbps would be feasible with respect to the FCC power constraints. With current low complexity UWB TR systems, the peak data rate is constrained to much lower values, because they are sensitive to intersymbol interference (ISI). Therefore, the impact of moderate ISI on symbolwise UWB TR detectors is investigated. It is shown that presented UWB TR scheme is robust to ISI and for a specific system setup even benefits from ISI. Due to this gain, the UWB TR scheme outperforms differential phase shift keying (DPSK) in presence of ISI and the FCC peak power constraint.
    Signals, Systems and Computers, 2007. ACSSC 2007. Conference Record of the Forty-First Asilomar Conference on; 12/2007
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    • "Measured WBAN channels show a path loss P L ≤ 60 dB and a moderate delay spread τ rms =10 ns. Due to stringent low complexity requirements, an orthogonal binary pulse position modulation (BPPM) is considered combined with an energy detector receiver [1]. The power spectral density of the transmit signal is smoothed by a randomized pulse polarity. "
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    ABSTRACT: A wireless body area network with an average throughput of 500 kbps based on ultra-wideband pulse position modulation is considered. For a long battery autonomy a hardware aware system optimization with respect to the specific applications at hand is essential. A key feature to achieve power savings is low duty cycle signaling, and its effectiveness when combined with burst-wise transmission at high peak data rate. Exploiting this observation, an ultra-low power system is presented, jointly optimized with respect to application and hardware specific aspects. Based on an exhaustive survey of the state of the art literature, its power consumption is estimated significantly below 1 mW.
    Ultra-Wideband, 2007. ICUWB 2007. IEEE International Conference on; 10/2007
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