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In this paper, we propose a novel cross layer scheme to lower power
consumption of ADCs in OFDM systems, which is based on resolution
adaptive ADCs and Fountain codes. The key part in the new proposed
system is that the dynamic range of ADCs can be reduced by
discarding the packets which are transmitted over 'bad' sub
carriers. Correspondingly, the...
Citations
... Above method is labeled as "Scheme I". A packet occupying a part of subcarriers and transmitting over a few symbols is the Scheme II [17]. Figure 2 illustrates mapping relationships of Scheme I and Scheme II. ...
... For WLAN systems, a fountain-encoded packet can be transmitted over a single sub-carrier [19]. Multiple packets are transmitted simultaneously by using frequency division multiplexing. ...
... With the same effective throughput (i.e. 21.6 Mbits/s), this new method offers us a SNR gain of 7.5 dB in comparison with the IEEE 802.11a system [19]. 5 ...
... WLAN system, the channel is considered to be timeinvariant over a MAC frame. The transmission of each fountain-encoded packet in [19] is completed within a MAC frame. Hence, the channel over a fountain-encoded packet transmission can be considered as a time-invariant flat fading channel. ...
... Partial channel estimation for OFDM using least square (LS) method (YiWang, Li, Zhang, & Liu1, 2009) is obtained using symmetric extension and also reduces the loss of power leakage in channel. A cross layer approach (Shao, Schiphorst, & Slump, 2009) can reduce power consumption up to 70% in analog-to-digital convertor (ADC) OFDMA systems. ...
Wireless heterogeneous environment is becoming increasingly popular because of its ability to support multi access technologies, which keeps the mobile users always connected. The fourth generation (4G) of wireless environment consists of dissimilar technologies like worldwide interoperability for microwave access (WiMAX) and long term evolution-advanced (LTE-A). Coexistence of these standards presents technological challenges. Other challenges towards heterogeneous 4G environment include coexistence of third generation (3G) and 4G and coexistence of wireless local area network (WLAN) and 3G/4G technologies. In this chapter, we present the technical overview of the 4G (WiMAX and LTE-A) standards and identify the challenges and research issues (i.e., mobility management, network selection, handover and Quality of Service [QoS]) toward a multi-access environment that consists of 3G, 4G and WLAN technologies. The chapter also discusses future directions and some research solutions.
... In other words, with the help of fountain codes, each transmitted packet becomes independent with respect to each other. By transmitting one fountainencoded packet over a single sub-carrier, this scheme allows us to discard some parts of wireless channel interfered by PBJ or in deep fading [11]. Fig. 1 shows how this cross coding approach works in OFDM systems. ...
... To achieve a high R F C with small block size, we choose to decode LT codes by using the combination of the message-passing algorithm [10] and Gaussian elimination. In this case, we can have R F C ≈ 0.97 for K ≥ 500 [11]. 1 LT codes are a kind of fountain codes [10]. ...
The performance of OFDM systems (e.g. IEEE 802.11g system) can severely degrade due to partial band interference (e.g. from Bluetooth devices). Therefore, we propose a novel cross coding scheme based on erasure codes to mitigate the effect of partial band jamming (PBJ). The key element of this coding scheme is to discard the part of channel that is corrupted by PBJ. By transmitting a packet over a single sub-carrier, the original data can be reconstructed with the assistance of erasure codes. In comparison with the Wiener beamforming technique, the proposed coding scheme has a power gain (i.e. at least 50% power saving) in the wireless receiver, and also has a performance gain in terms of the corrupted bandwidth and SIR. At SIR = 0 dB, it endures 1 MHz larger corrupted bandwidth than using beamforming, allowing one more Bluetooth device to coexist with the IEEE 802.11g system. Furthermore, it has a SIR gain of around 4 dB over the beamforming algorithm when only one Bluetooth interferes the IEEE 802.11g system (i.e. the corrupted bandwidth = 1 MHz).
... where ε is the percentage of extra packets and is called the overhead. To achieve a low ε with small block size, we choose to decode the LT code by using the combination of the message-passing algorithm and Gaussian elimination [9]. ...
Spectral Minutiae (SM) representation enables the combination of minutiae-based fingerprint recognition systems with template protection schemes based on fuzzy commitment, but it requires error-correcting codes that can handle high bit error rates (i.e. above 40%). In this paper, we propose a 3-Layer coding scheme based on erasure codes for the SM-based biometric recognition system. Our approach is inspired by the fact that the Packet Error Rate (PER) is proportional to the Bit Error Rate (BER). Each packet is encoded by an Error Detection Code (EDC) and an Error Correction Code (ECC). The packet can only survive if it successfully passes the ECC and EDC decoder. With the erasure code, the system can reconstruct the secret key by only using the survived packets. By applying SM to the FVC2000-DB2 fingerprint database, the unprotected system achieves an EER of around 6% while our proposed coding scheme reaches an EER of approximately 6.5% with a 1032-bit secret key.
... Here, we call opportunistic error correction based on Option I as OEC-I and the one with Option II as OEC-II. In [8] , we have investigated the performance of OEC-I. With the same throughput, simulation results showed that OEC-I saves more than 70% of energy in ADCs comparing to the IEEE 802.11a system [8]. ...
... In [8] , we have investigated the performance of OEC-I. With the same throughput, simulation results showed that OEC-I saves more than 70% of energy in ADCs comparing to the IEEE 802.11a system [8]. However, the performance of OEC-II is still not clear. ...
... The messagepassing algorithm has a linear computation cost [6], but it requires a large ε for small block size. For example, the practical overhead of LT codes is 14% when K = 2000, which limits its application in the practical system [8]. By combining the message-passing algorithm with Gaussian elimination, the overhead of LT codes is reduced to 3% when K ≥ 500 [8]. ...
In this paper, we propose an energy-efficient error correction scheme to lower the power consumption of the ADCs in the OFDM system. The proposed opportunistic error correction scheme is based on resolution adaptive ADCs and fountain codes. The key idea is to reduce the dynamic range of the channel by discarding part of the channel in deep fading. Correspondingly, the power consumption in ADCs can be decreased. In our approach, each sub-carrier transports a fountain-encoded packet. The receiver only decodes fountain-encoded packets with high SNR. Others are discarded. To compensate for the discarded packets, a high order modulation is used. The new error correction layer does not require perfect channel knowledge, so it can be applied in a real system. With our approach and 16-QAM, the energy consumption in ADCs is reduced by around 73% with non-perfect channel estimation comparing to the traditional IEEE 802.11a system under the same channel conditions and throughput.
... For example, the practical overhead of LT codes is 14% when K = 2000, which limits its application in the practical system [13]. In [10], we have shown that the overhead is reduced to 3% by combining the messaging-passing algorithm and Gaussian elimination to decode LT codes for K ≥ 500 at the expense of a higher complexity. ...
... The performance of OEC-I (i.e. to exchange the code rate of error correcting codes with the discarded sub-carriers) has been studied in [10]. With the same effective throughput, OEC-I has a SNR gain of around 7.5 dB comparing to the conventional 802.11a system. ...
... Here, we call opportunistic error correction based on Option I as OEC-I and the one with Option II as OEC-II. In [10], we have investigated the performance of OEC-I. With the same throughput, simulation results showed that OEC-I has a SNR gain of 7.5 dB comparing to the IEEE 802.11a system [10]. ...
In wireless OFDM-based systems, coding jointly over all the sub-carriers simultaneously performs better than coding separately per sub-carrier. However, the joint coding is not always optimal because its achievable channel capacity (i.e. the maximum data rate) is inversely proportional to the dynamic range of the channel. In this paper, we propose a novel cross coding scheme to increase the maximum data rate (i.e. the noise floor) achieved in frequency selective channels. The proposed OEC-II is based on fountain codes. The key element in OEC-II is to exchange the modulation order with the discarded subcarriers. In such case, the system can increase the noise floor by only taking care of the sub-carriers with high energy. By transmitting a fountain-encoded packet over a single sub-carrier, the packets can be discarded if they have encountered a low-energy channel. Fountain codes can recover the source data by only using the surviving packets. With the same effective transmission data rate (i.e. 10.8 Mbits/s), OEC-II with QAM-16 has a SNR gain of around 7 dB over the FEC layer from the IEEE 802.11a standard, around 8 dB over the FEC layer from the IEEE 802.11n standard, around 7 dB over OEC-II with QPSK and around 3 dB over OEC-II with QAM-64.
... In [1], we have proposed a novel error correction layer based on adaptive ADCs and fountain codes to mitigate the effects of a wireless channel at a lower power consumption level in ADCs comparing to traditional solutions. With this method, the resolution of ADCs is adapted to each channel condition instead of fixing to the high-resolution for the worsecase scenario. ...
... The performance of this new scheme has been investigated by the C++ simulation in [1]. With the same effective throughput, the simulation results have shown that this new algorithm allows a reduction of more than 70% power consumption in ADCs comparing to the traditional IEEE 802.11a system [1]. ...
... The performance of this new scheme has been investigated by the C++ simulation in [1]. With the same effective throughput, the simulation results have shown that this new algorithm allows a reduction of more than 70% power consumption in ADCs comparing to the traditional IEEE 802.11a system [1]. C++ simulation, with its highly accurate double-precision numerical environment, is on the one hand a perfect tool for the investigation of the algorithms. ...
In, we have proposed a novel cross-layer scheme based on resolution adaptive ADCs and fountain codes for the OFDM systems to lower the power consumption in ADCs. The simulation results show that it saves more than 70% power consumption in ADCs comparing to the current IEEE 802.11a system. In this paper, we investigate its performance in the realworld. Measurement results show that the FEC layer used in the IEEE 802.11a system consumes around 59 times of the amount of power in ADCs comparing to the LDPC codes from the IEEE 802.11n standard, whose power consumption in ADCs is around 26 times of the proposed cross-layer method. In addition, this new cross-layer approach only needs to process the well-received packets to save the processing power. The latter can not be applied in the current FEC schemes.
... We have shown that decoding the fountain codes using the message-passing algorithm combined with Gaussian elimination allows small block sizes, e.g. K = 500, with small overhead ε = 3% in [58]. Small block sizes are needed to keep the decoding delay low, which is important in real-time applications such as mobile TV. ...
... Each burst is encoded by a LT code (with parameters c = 0.03, σ = 0.3) and decoded by the message-passing algorithm and Gaussian elimination together. From [58], we know that 3% overhead is required to recover the source packets successfully. To each fountain-encoded packet, a 7-bit CRC is added then the (255,175) LDPC encoder is applied. ...
The wireless channel is a hostile environment. The transmitted signal does not only suffers multi-path fading but also noise and interference from other users of the wireless channel. That causes unreliable communications. To achieve high-quality communications, error correcting coding is required to mitigate the noise and interference encountered during the signal transmission. However, the current design of error correcting codes does not take the power consumption in ADCs into account. ADCs consume about 50\% of the total base-band power. The power-efficiency of ADCs does not increase in the same speed as the baseband signal processing. Digital signal processing follows Moore's law. Given the same specification, the power consumed in ADCs halves every 2.7 years but the power consumption in the baseband signal processing decreases a factor of 10 every 5 years. In the case of RF signal processing, the power efficiency is limited by the semi-conductor technology. Therefore, ADCs are the main bottleneck for an energy-efficient wireless receiver. Quantized channels arise in ...
... low delay) [10]. In [11], the authors have shown that the small block size (i.e. K = 500) of LT codes with small ε (i.e. ...
... Combining both methods for decoding can have lower overhead and higher computation complexity in comparison with only using the message-passing algorithm to decode. For K = 500, the complexity of using both methods is around of 25% of the complexity of only using messagepassing decoding, but the overhead of using both methods can be reduced from 42% to 3% [11]. In this paper, we combine both methods to decode LT codes. ...
... For the case of FEC III and IV, each burst is encoded by a LT code (with parameters c = 0.03, σ = 0.3) and decoded by the message-passing algorithm and Gaussian elimination together. From [11], we know that 3% overhead is required to recover the source packets successfully. To each fountainencoded packet, a 7-bit CRC is added, then the (175,255) LDPC encoder is applied. ...
In wireless OFDM-based systems, coding jointly over all the sub-carriers simultaneously performs better than coding separately per sub-carrier. However, the joint coding is not always optimal. In this paper, we propose a novel coding scheme based on fountain codes, which combines the separate coding and the joint coding over all the sub-carriers. The key element in the new proposed system is that each fountain-encoded packet is transmitted over a single sub-carrier. The packets can be discarded if they have encountered a low-energy channel. Fountain codes can recover the source data by using only the surviving packets. With this new approach, we have a gain of around 8.5 dB comparing to the FEC layer used in current WLAN standards (i.e. the IEEE 802.11a standard and the IEEE 802.11n standard).
