We consider secure multi-terminal source coding problems in the presence of a public helper. Two main scenarios are studied: 1) source coding with a helper where the coded side information from the helper is eavesdropped by an external eavesdropper, 2) triangular source coding with a helper where the helper is considered as a public terminal. We are interested in how the helper can support the source transmission subject to a constraint on the amount of information leaked due to its public nature. We characterize the tradeoff between transmission rate, incurred distortion, and information leakage rate at the helper/eavesdropper in the form of a rate-distortion-leakage region for various classes of problems.

We consider the Wyner-Ziv and two way source coding problems with the erasure distortion measure. We characterize the rate-distortion regions for these settings, when the source and side information satisfy a positivity condition. Using our results, we show that, contrary to recent conjectures in the literature, feedback from the decoder to the encoder does not reduce the overall rate required in the Wyner-Ziv setting with erasure distortion, when the positivity condition is satisfied. Finally, we extend our techniques to characterize the rate-distortion regions of two multiterminal source coding settings, the Heegard-Berger setting, and the cascade source coding setting, when the positivity condition is satisfied.

This paper shows that the Maddah-Ali–Tse (MAT) scheme, which achieves the symmetric capacity of two example broadcast channels with strictly causal state information at the transmitter, is a simple special case of the Shayevitz–Wigger (SW) scheme for the broadcast channel with generalized feedback, which involves block Markov coding, Gray–Wyner compression, superposition coding, and Marton coding. Focusing on the class of symmetric broadcast channels with state, we derive an expression for the maximum achievable symmetric rate using the SW scheme. We show that the MAT results for the two-receiver case can be recovered by evaluating this expression for the special case in which superposition coding and Marton coding are not used. We then introduce a new broadcast channel example that shares many features of the MAT examples. We show that another special case of our maximum symmetric rate expression in which superposition coding is also used attains a higher symmetric rate than the MAT scheme. The symmetric capacity of this new example is not known, however.

We consider the problems of secure lossy source coding with side information in the presence of a passive eavesdropper who has access to the source description. The encoder wishes to compress the source sequence in order to satisfy a distortion criterion at the decoder, while revealing only limited knowledge about the source to the eavesdropper. The side information available to the encoder, the legitimate decoder, or the eavesdropper can be influenced by a cost-constrained action sequence. Three different settings are studied. In the first two settings, we are interested in understanding the influence of the action sequence on the rate-distortion-leakage tradeoff where the action is taken either by the decoder or by the encoder to influence side information at the decoder and eavesdropper. Next, we consider a setting where common action-dependent side information is available securely to both encoder and decoder, and thus can be used for secret key generation. We characterize the optimal rate-distortion-cost-leakage region or the corresponding inner bounds for a discrete memoryless source for above settings. The results are useful in characterizing fundamental limits for example in secure sensor networking and future cyber physical systems.

This paper proposes a general model for offloading to an access point (AP) to minimize energy cost in a heterogeneous network with a renewable-energy powered base station (BS) that is connected to a microgrid. We consider the setting where both the BS and the AP can buy energy from the grid to satisfy their requirements, but the BS can sell back any excess renewable energy to the grid. The downlink scenario is considered whereby the BS and the AP cooperate to serve a set of users, and the problem is to determine the user assignment to the BS or the AP. In the specific case of time division multiple access, we show that the optimal user assignment problem is NP Hard. We propose a sub-optimal, low complexity algorithm for this setting and obtain an approximation guarantee to the worst case sub-optimality of our algorithm. Simulations show that our algorithm performs well, with only a small gap to the optimal exhaustive search method over the set of users.

In this paper, the sum-rate of a cognitive multiple access channel (C-MAC) is studied, where a secondary network (SN) with multiple secondary users (SUs) transmitting to a secondary base station (SBS) shares the spectrum band with a primary user (PU). An interference power constraint (IPC) is imposed on the SN to protect the PU. Under the IPC and the individual transmit power constraint (TPC) imposed on each SU, we investigate the power allocation strategies to maximize the sum-rate of the C-MAC without successive interference cancellation (SIC). We prove that the optimal solution must be at the extreme points of the feasible region. We show that Dynamic Time Division Multiple Access (D-TDMA) is optimal with high probability when the number of SUs is large. Furthermore, we show through simulations that the optimal power allocation to maximize the sum-rate of the C-MAC with SIC is optimal or near-optimal for our setting when D-TDMA is not optimal.

In this paper, we investigate resource allocation strategies for a point-to-point wireless communications system with hybrid energy sources consisting of an energy harvester and a conventional energy source. By assuming that the non-causal information of the energy arrivals and the channel power gains is known, a mixed integer programming problem is formulated to minimize the total energy cost of such a system over N fading slots under the energy harvesting constraints and a proposed outage constraint. The outage constraint requires that a minimum fraction of slots to be reliably decoded. This constraint is useful if, for example, an outer code is used to recover that all data bits. Optimal linear time algorithms are obtained for two extreme cases: when the number of outage slots is 1 or N -1. For the general case, a lower bound based on linear programming relaxation, and two suboptimal algorithms are proposed. Numerical simulations indicate that the proposed suboptimal algorithms exhibit only a small gap from the lower bound for a wide range of given parameters.

We consider the Heegard-Berger source coding problem with multiple decoders, and list decoding constraints for some of the decoders. The decoders with list decoding constraint output a list of likely source sequences and we desire the true source sequence to be in the list with high probability. When list decoding constraints are imposed on all decoders, we characterize the rate-list size region for arbitrary distributed source and side informations. For the two decoders setting with list decoding constraint on one decoder and per-symbol distortion constraint on the other, we characterize the rate-distortion-list size region when the side information of the decoder with per-symbol distortion constraint is less noisy than the side information of the list decoding decoder. We then extend this result to a three decoders setting. For the case where the side information of the list decoding decoder is less noisy than the side information of the decoder with per-symbol distortion constraint, we characterize the rate-distortion-list size region under an additional common reconstruction constraint at the encoder.

We consider the Wyner-Ziv and two way source coding problems with the erasure distortion measure. We characterize the rate-distortion regions for these settings when the source and side information satisfy a positivity condition. Using our results, we show that, contrary to recent conjectures in the literature, feedback from the decoder to the encoder does not reduce the overall rate required in the Wyner-Ziv setting with erasure distortion, when the positivity condition is satisfied. Finally, we extend our techniques to characterize the rate-distortion region of a Cascade source coding setting when the positivity condition is satisfied.

We consider uplink WiFi data offloading in a heterogeneous network consisting of one LTE macrocell and one overlaid 802.11n WiFi hotspot to maximize the minimum energy efficiency (EE) of the users. We propose a closed-form expression to compute Nw, i.e., the number of offloaded users, and then offload the data traffic of Nw users with the lowest received SINR at the cellular base station (BS) to the WiFi network. Our simulation results show that our proposed offloading algorithm performs nearly the same as the exhaustive search and greedy algorithms, but requires much lower computational complexity. We also compare the EE performance of our proposed algorithm with naive schemes, i.e., no offloading, all offloading, and random selection, by taking into account the practical energy cost such as the transmit-power dependent energy consumption in LTE and the contention energy consumption in WiFi. We show that our proposed algorithm always outperforms naive schemes, especially when the user density in the hotspot is high.

We consider the setting where actions can be used to modify a state sequence before compression. The minimum rate needed to losslessly describe the optimal modified sequence is characterized when the state sequence is either noncausally or causally available at the action encoder. The achievability is closely related to the optimal channel coding strategy for channel with states. We also extend the analysis to the lossy case.

In this paper, we propose a model for energy cooperation between cellular base stations (BSs) with individual hybrid power supplies (including both the conventional grid and renewable energy sources), limited energy storages, and connected by resistive power lines for energy sharing. When the renewable energy profile and energy demand profile at all BSs are deterministic or known ahead of time, we show that the optimal energy cooperation policy for the BSs can be found by solving a linear program. We show the benefits of energy cooperation in this regime. When the renewable energy and demand profiles are stochastic and only causally known at the BSs, we propose an online energy cooperation algorithm and show the optimality properties of this algorithm under certain conditions. Furthermore, the energy-saving performances of the developed offline and online algorithms are compared by simulations, and the effect of the availability of energy state information (ESI) on the performance gains of the BSs' energy cooperation is investigated. Finally, we propose a hybrid algorithm that can incorporate offline information about the energy profiles, but operates in an online manner.

In this paper, we investigate resource allocation strategies for a point-to-point wireless communications system with hybrid energy sources consisting of an energy harvester and a conventional energy source. In particular, as an incentive to promote the use of renewable energy, we assume that the renewable energy has a lower cost than the conventional energy. Then, by assuming that the non-causal information of the energy arrivals and the channel power gains are available, we minimize the total energy cost of such a system over N fading slots under a proposed outage constraint together with the energy harvesting constraints. The outage constraint requires a minimum fixed number of slots to be reliably decoded, and thus leads to a mixed-integer programming formulation for the optimization problem. This constraint is useful, for example, if an outer code is used to recover all the data bits. Optimal linear time algorithms are obtained for two extreme cases, i.e., the number of outage slot is 1 or N - 1. For the general case, a lower bound based on the linear programming relaxation, and two suboptimal algorithms are proposed. It is shown that the proposed suboptimal algorithms exhibit only a small gap from the lower bound. We then extend the proposed algorithms to the multi-cycle scenario in which the outage constraint is imposed for each cycle separately. Finally, we investigate the resource allocation strategies when only causal information on the energy arrivals and only channel statistics is available. It is shown that the greedy energy allocation is optimal for this scenario.

WiFi offloading is regarded as one of the most promising techniques for dealing with the explosive data increase in cellular networks due to its high data transmission rate and low requirement on devices. In this paper, we investigate the mobile data offloading problem through a third-party WiFi access point (AP) for a cellular mobile system. From the cellular operator's perspective, by assuming a usage-based charging model, we formulate the problem as a utility maximization problem. In particular, we consider three scenarios: 1) successive interference cancellation (SIC) available at both the base station (BS) and the AP; 2) SIC available at neither the BS nor the AP; and 3) SIC available at only the BS. For scenario 1, we show that the utility maximization problem can be solved by considering its relaxation problem, and the proposed data offloading scheme is near-optimal when the number of users is large. For scenario 2, we prove that with high probability the optimal solution is One-One-Association, i.e., one user connects to the BS and one user connects to the AP. For scenario 3, we show that with high probability there is at most one user connecting to the AP, and all the other users connect to the BS. By comparing these three scenarios, we prove that SIC decoders help the cellular operator maximize its utility. To relieve the computational burden of the BS, we propose a threshold-based distributed data offloading scheme. We show that the proposed distributed scheme performs well if the threshold is properly chosen.

In this paper, we consider a distributed transmitter (D-TX) system, in which each TX has a dissimilar power amplifier with different maximum output power, and different number of transmit antennas. To improve energy efficiency (EE) of the D-TX system, we design a multiuser multiple-input multiple-output (MU-MIMO) precoding matrix, a transmit antenna selection (AS) matrix, and a power control (PC) matrix. A conventional zero-forcing based MU-MIMO precoding is shown to be EE optimal for given AS and PC. Optimal and heuristic PC methods are proposed for given AS and MU-MIMO precoding. For the AS, we also propose heuristic algorithms. Average transmit power, outage probability, and EE performance are evaluated to compare three AS algorithms, and to observe the performance gap between the optimal and heuristic PC methods. From the numerical results, we discuss a tradeoff between AS complexity and EE performance and provide a useful guide for energy efficient D-TX system design.

We consider a secure source coding problem with side informations at the decoder and the eavesdropper. The encoder has a source that it wishes to describe with limited distortion through a rate-limited link to a legitimate decoder. The message sent is also observed by the eavesdropper. The encoder aims to minimize both the distortion incurred by the legitimate decoder; and the information leakage rate at the eavesdropper. When the encoder has access to the side information (S.I.) at the decoder, we characterize the rate-distortion-information leakage rate (R.D.I.) region under a Markov chain assumption and when S.I. at the encoder does not improve the rate-distortion region as compared to the case when S.I. is absent. We then extend our setting to consider the case where the encoder and decoder obtain coded S.I. through a rate-limited helper, and characterize the R.D.I. region for several special cases under logarithmic loss distortion (log-loss). Finally, we consider the case of list or entropy constraints at the decoder and show that the R.D.I. region coincides with R.D.I. region under log-loss.

We consider secure multi-terminal source coding problems in the presence of a public helper. Two main scenarios are studied: 1) source coding with a helper where the coded side information from the helper is eavesdropped by an external eavesdropper, 2) triangular source coding with a helper where the helper is considered as a public terminal. We are interested in how the helper can support the source transmission subject to a constraint on the amount of information leaked due to its public nature. We characterize the tradeoff between transmission rate, incurred distortion, and information leakage rate at the helper/eavesdropper in the form of a rate-distortion-leakage region for various classes of problems.

In this paper, we study the power consumption in relay networks of the 60 GHz wireless communication based on amplify-and-forward (AF) and decode-and-forward (DF) relaying strategies. We propose a total power consumption model including drive power, decoding power, and power consumption of power amplifier (PA). This model is formulated as a function of drive power, which gives an easy access to the system level optimisation. The optimal drive power that minimises the total power consumption while satisfying the performance requirement can be found by numerical searching method. The impact of relay's locations on the total power consumption is also investigated. We show that, with the same performance requirement, in the small source-relay separation case AF consumes less power than DF, while with larger separation, AF consumes significantly more power than DF. This is different from the common intuition that DF is always more power consuming than AF due to the extra decoding power consumption at relay, which is due to the fact that the large source-relay separation limits the effective destination signal-to-noise ratio (SNR) in AF, leading to more substantial decoding power consumption in the many more decoding iterations than DF.

In this paper, we propose a model for energy cooperation between cellular base stations (BSs) with individual renewable energy sources, limited energy storages and connected by resistive power lines for energy sharing. When the renewable energy profile and energy demand profile at all BSs are deterministic or known ahead of time, we show that the optimal energy cooperation policy for the BSs can be found by solving a linear program. We show the benefits of energy cooperation in this regime. When the renewable energy and demand profiles are stochastic and only causally known at the BSs, we propose an online energy cooperation algorithm and show the optimality properties of this algorithm under certain conditions. Furthermore, the energy-saving performances of the developed offline and online algorithms are compared by simulations, and the effect of the availability of energy state information (ESI) on the performance gains of the BSs' energy cooperation is investigated.

We consider multiterminal source coding with a single encoder and multiple decoders where either the encoder or the decoders can take cost-constrained actions which affect the quality of the side information present at the decoders. For the scenario where decoders take actions, we characterize the rate-cost tradeoff region for lossless source coding, and give an achievability scheme for lossy source coding for two decoders which is optimum for a variety of special cases of interest. For the case where the encoder takes actions, we characterize the rate-cost tradeoff for a class of lossless source coding scenarios with multiple decoders. Finally, we also consider extensions to other multiterminal source coding settings with actions, and characterize the rate-distortion-cost tradeoff for a case of successive refinement with actions.

We consider the problem of estimating a signal corrupted by independent interference with the assistance of a cost-constrained helper who knows the interference causally or noncausally. When the interference is known causally, we characterize the minimum distortion incurred in estimating the desired signal. In the noncausal case, we present a general achievable scheme for discrete memoryless systems and novel lower bounds on the distortion for the binary and Gaussian settings. Our Gaussian setting coincides with that of assisted interference suppression introduced by Grover and Sahai. Our lower bound for this setting is based on the relation recently established by Verdú between divergence and minimum mean squared error. We illustrate with a few examples that this lower bound can improve on those previously developed. Our bounds also allow us to characterize the optimal distortion in several interesting regimes. Moreover, we show that causal and noncausal estimation are not equivalent for this problem. Finally, we consider the case where the desired signal is also available at the helper. We develop new lower bounds for this setting that improve on those previously developed, and characterize the optimal distortion up to a constant multiplicative factor for some regimes of interest.

We consider the problem of estimating a signal corrupted by independent interference in which the estimator (decoder) is aided by a helper (encoder) with a limited power budget that has knowledge of the interfering signal noncausally. In the Gaussian case, this problem is equivalent to the problem of Assisted Interference Suppression considered by Grover and Sahai and we obtain an improved lower bound for this problem using Verdú's relationship between mismatched estimation and relative entropy. We also extend our analysis to consider the case when the signal to be estimated, in addition to the interference, is known to the helper. We establish a lower bound that improves on those recently derived by Huang and Narayanan.

This paper establishes inner bounds on the secrecy capacity regions for the general three-receiver broadcast channel with one common and one confidential message sets. We consider two setups. The first is when the confidential message is to be sent to two receivers and kept secret from the third receiver. Achievability is established using indirect decoding, Wyner wiretap channel coding, and the new idea of generating secrecy from a publicly available superposition codebook. The inner bound is shown to be tight for a class of reversely degraded broadcast channels and when both legitimate receivers are less noisy than the third receiver. The second setup investigated in this paper is when the confidential message is to be sent to one receiver and kept secret from the other two receivers. Achievability in this case follows from Wyner wiretap channel coding and indirect decoding. This inner bound is also shown to be tight for several special cases.

A lower bound on the secrecy capacity of the wiretap channel with state information available causally at both the encoder and the decoder is established. The lower bound is shown to be strictly larger than that for the noncausal case by Liu and Chen. Achievability is proved using block Markov coding, Shannon strategy, and key generation from common state information. The state sequence available at the end of each block is used to generate a key to enhance the transmission rate of the confidential message in the following block. An upper bound on the secrecy capacity when the state is available noncausally at the encoder and the decoder is established and is shown to coincide with the aforementioned lower bound for several classes of wiretap channels with state.

In this paper, we consider the cascade and triangular rate-distortion problems where the same side information is available at the source node and user 1, and the side information available at user 2 is a degraded version of the side information at the source node and user 1. We characterize the rate-distortion region for these problems. For the cascade setup, we show that, at user 1, decoding and rebinning the codeword sent by the source node for user 2 is optimum. We then extend our results to the two-way cascade and triangular setting, where the source node is interested in lossy reconstruction of the side information at user 2 via a rate limited link from user 2 to the source node. We characterize the rate-distortion regions for these settings. Complete explicit characterizations for all settings are given in the quadratic Gaussian case. We conclude with two further extensions: a triangular source coding problem with a helper, and an extension of our two-way cascade setting in the quadratic Gaussian case.

We consider multi-terminal source coding with a single encoder and multiple decoders where either the encoder or the decoders can take actions which affect the quality or availability of the side information present at the decoders, subjected to an additional cost constraint on the actions taken. For the scenario where a joint action is taken at the decoders, we characterize the rate-cost trade-off region for lossless source coding, and give an achievability scheme for lossy source coding for two decoders which is optimum for several special cases. For the case where the encoder takes actions, we characterize the rate-cost trade-off for a class of lossless source coding scenarios with multiple decoders.

We consider cascade and triangular source coding with side information and causal reconstruction at the end node. When the side information at the source and intermediate nodes are the same, we characterize the rate distortion regions for both the cascade and triangular source coding problems. For the general cascade setting with causal reconstruction at the end node, we characterize the rate region when the sources satisfy a positivity condition, or when a Markov chain holds.

A lower bound on the secrecy capacity of the wiretap channel with state information available causally at both the encoder and decoder is established. The lower bound is shown to be strictly larger than that for the noncausal case by Liu and Chen. Achievability is proved using block Markov coding, Shannon strategy, and key generation from common state information. The state sequence available at the end of each block is used to generate a key, which is used to enhance the transmission rate of the confidential message in the following block. An upper bound on the secrecy capacity when the state is available noncausally at the encoder and decoder is established and is shown to coincide with the lower bound for several classes of wiretap channels with state.

Achievable secrecy rate regions for the general 3-receiver broadcast channel with one common and one confidential message sets are established. We consider two setups: (i) when the confidential message is to be sent to two of the receivers and the third receiver is an eavesdropper; and (ii) when the confidential message is to be sent to one of the receivers and the other two receivers are eavesdroppers. We show that our secrecy rate regions are optimum for some special cases.