End-to-End Resource Allocation in OFDM Based Linear Multi-Hop Networks

Abstract

Abstract-We study the end-to-end resource allocation in an OFDM based multi-hop network consisting of a one-dimensional chain of nodes including a source, a destination, and multiple relays. The problem is to maximize the end-to-end average transmission rate under a long-term total power constraint by adapting the transmission power on each subcarrier over each hop and the transmission time used by each hop in every time frame. The solution to the problem is derived by decomposing it into two subproblems: short-term time and power allocation given an arbitrary total power constraint for each channel realization, and total power distribution over all channel realizations. We show that the optimal solution has the following features: the power allocation on subcarriers over each hop has the water-filling structure and a higher water level is given to the hop with relatively poor channel condition; meanwhile, the fraction of transmission time allocated to each hop is adjusted to keep the instantaneous rates over all hops equal. To tradeoff between performance, computational complexity and signalling overhead, three suboptimal resource allocation algorithms are also proposed. Numerical results are illustrated under different network settings and channel environments.

Jointly Optimal Channel Pairing and Power Allocation for Multichannel Multihop Relaying

“…This interesting observation suggests that, because of CP, at moderately high SNR, we are able to reduce the centralized PA solution to a simple uniform PA which requires no global channel information without losing much optimality. Note that the same argument is applicable to DF relaying, but the optimal PA approaches to a uniform allocation at a much slower rate than that for AF, which can be shown by comparing (16) and (18). The range of SNR values under consideration is too small to see the same effect in Fig.…”

“…The authors of [17] proposed an adaptive PA algorithm to maximize the end-to-end rate under the total power constraint in a multihop OFDM relaying system. For a similar network with DF relaying, [18] studied the problem of joint power and time allocation under the long-term total power constraint to maximize the end-to-end rate. Furthermore, in [17], the idea of using CP to further enhance the performance was mentioned in addition to PA.…”

“…It is obtained using the upper bound approximation of equivalent SNR in (2) over a path. The power allocated to each transmitting node on path is given by (18) The PA solution in (14) requires global channel gain information and therefore needs to be implemented in a centralized fashion.…”

“…Thus, the total power is approximately equally distributed to different paths. The power on each path is then further assigned optimally to each channel on the path according to (18), which is typically not uniform. The exception is when each hop exhibits a similar channel gain.…”

End-to-end outage minimization in OFDM based linear relay networks

“…In [5], Oyman et al summarized the end-to-end capacity results of a multi-hop relay network under fixed-rate and rate-adaptive relaying strategies, and further illustrated the merits of multi-hop relaying in cellular mesh networks. Authors in [9] studied the per-hop transmission time and subcarrier power allocation problem in the OFDM based linear multi-hop relay network to maximize the end-to-end average transmission rate under a long-term total power constraint. However, the end-to-end average rate can only be obtained 3 at the expense of large delay.…”