Energy-efficient link adaptation in frequency-selective channels

Abstract

Energy efficiency is becoming increasingly important for small form factor mobile devices, as battery technology has not kept up with the growing requirements stemming from ubiquitous multimedia applications. This paper addresses link adaptive transmission for maximizing energy efficiency, as measured by the "throughput per Joule" metric. In contrast to the existing water-filling power allocation schemes that maximize throughput subject to a fixed overall transmit power constraint, our scheme maximizes energy efficiency by adapting both overall transmit power and its allocation, according to the channel states and the circuit power consumed. We demonstrate the existence of a unique globally optimal link adaptation solution and develop iterative algorithms to obtain it. We further consider the special case of flat-fading channels to develop an upper bound on energy efficiency and to characterize its variation with bandwidth, channel gain and circuit power. Our results for OFDM systems demonstrate improved energy savings with energy optimal link adaptation as well as illustrate the fundamental tradeoff between energy-efficient and spectrum-efficient transmission.

Fuzzy Logic Based Fault Detection in Distributed Sensor Networks

“…The energy of node "E" is [21]: E = E N × d i (4) Assume "L eff " is the link efficiency for the nodes in the network:…”

A context-aware approach to wireless transmission adaptation

“…A good understanding of the energy consumption of wireless NICs operating in a flexible communication environment helps us to identify the space for improvement of the energy efficiency of the whole system. A bit of information over a single subcarrier i is transmitted with energy: (3) E T x,i = P T x,i + P T C R i where P T x,i represents the transmission power and P T C the transceiver circuit power of a wireless NIC [15]. The transceiver circuit power is constant irrespective of the transmission parameters and represents the power needed to keep the digital circuits powered whenever the NIC is in the transmission mode.…”

“…Our approach to channel width change is similar to Jello [26] and 802.22 [12]: we change the width by OFDM subcarrier (de)activation and bind the available spectrum into a single OFDM channel, even if the available spectrum resides in non-contiguous bands. 1 In spite of a substantial body of related academic work that analyzes each of the individual parameters separately [11], [15], [20], it is unclear how concurrent adjustments of all the PHY knobs should be approached so that the solution is identified with minimum communication and processing overhead. In our initial analysis we show that tuning these parameters changes energy efficiency, packet delivery and spectrum utilization of a system.…”

Low‐complexity energy‐efficient resource allocation for delay‐tolerant two‐way orthogonal frequency‐division multiplexing relays

“…Previous work has largely focused on the optimization for spectral efficiency (SE) [16][17][18], however, the optimal point of SE is not necessarily equivalent to that of EE [19], so the optimization of EE under different scenarios is another significant problem we should consider. In the past, EE optimization of direct links was analyzed in [4] and [20]. In [4], the EE is optimized in frequency-selective channels using multi-carriers, where the constraints of sum rate and total power consumption including circuit power were considered.…”

“…In the past, EE optimization of direct links was analyzed in [4] and [20]. In [4], the EE is optimized in frequency-selective channels using multi-carriers, where the constraints of sum rate and total power consumption including circuit power were considered. In [20], the downlink and uplink of orthogonal frequency-division multiplexing access (OFDMA) networks with QoS and fairness issues were considered.…”