In this paper, we propose a novel precoded non-orthogonal frequency division multiplexing (NOFDM) with subcarrier index modulation (SIM) to increase spectral efficiency for multicarrier systems. The proposed NOFDM-SIM scheme is constituted by a filterbank multicarrier system under reduced subcarrier spacing, where precoded index modulated symbols are mapped onto the subcarriers. The detrimental effects of inter-carrier interference (ICI) resulting from the non-orthogonality between subcarriers are efficiently mitigated with the aid of eigenvalue-decomposition-based precoding. Our simulation results demonstrate that the proposed precoded NOFDM-SIM system exhibits a similar peak-to-average power ratio to OFDM and OFDM-SIM counterparts while achieving the bit error rate limit of zero-ICI OFDM in a channel-uncoded setting. We analyze the power spectral density of the proposed scheme to demonstrate that the proposed scheme is strictly bandlimited, unlike its orthogonal counterpart. Furthermore, we present detailed investigations of the effects on ICI in the proposed scheme with and without precoding as well as power allocation. Finally, we introduce a three-stage iterative decoding architecture for our proposed scheme and show near-capacity error performance.

In this paper, we propose a novel precoded faster-than-Nyquist (FTN) signaling scheme with power-domain-multiplexing in non-orthogonal multiple access (NOMA) down-link for tapping the joint benefits of high spectral efficiency and simultaneous multiuser connectivity. Non-orthogonality is introduced in both the symbol-interval (time) domain as well as in the multiple-access (power) domain to achieve a flexible resource allocation. Eigendecomposition of the FTN-specific intersymbol interference (ISI) matrix is used to achieve efficient cancellation of ISI, while successive interference cancellation is used to elim-inate multiuser interference induced by NOMA. We derive the achievable analytical rate bound and demonstrate the numerical results of the bit error rate performance for the proposed scheme.

In this paper, we propose a novel precoded non-orthogonal frequency division multiplexing (NOFDM) with sub-carrier index modulation (SIM) to increase spectral efficiency for multicarrier systems. The proposed NOFDM-SIM scheme is constituted by a filterbank multicarrier system under reduced subcarrier spacing, where precoded index modulated symbols are mapped onto the subcarriers. The detrimental effects of inter-carrier interference (ICI) resulting from the non-orthogonality between subcarriers are efficiently mitigated with the aid of eigenvalue-decomposition-based precoding. Our simulation results demonstrate that the proposed precoded NOFDM-SIM system exhibits a similar peak-to-average power ratio to OFDM and OFDM-SIM counterparts while achieving the bit error ratio limit of zero-ICI OFDM.

In this paper, we propose a precoded faster-than-Nyquist (FTN) signaling technique for time-domain single-carrier index-modulated symbol transmission. More precisely, eigenvalue decomposition (EVD) precoding is adopted for the FTN transmission of data bits modulated by single-carrier time-domain index modulation (IM). While the FTN scheme increases the spectral efficiency and data rate by increasing the density of transmit symbols, the time-domain IM works towards the same objective while maintaining symbol sparsity. We analytically derive the constrained capacity of the proposed system. Our simulation results show that the proposed scheme has better bit error ratio (BER) performance than the conventional FTN-IM scheme, particularly for the scenario of a higher packing ratio. With the proposed scheme, a 2.5 dB performance gain is observed at the BER of 10−4, where the packing ratio is 0.7 and the roll-off factor is 0.5 in the channel-uncoded scenario. We further analyze our scheme’s performance by characterizing its minimum Euclidean distance and inter-symbol interference. Furthermore, we present a three-stage serially concatenated iterative detection architecture for the proposed EVD-FTN-IM signaling scheme. It is demonstrated in our simulations that a near-capacity BER performance is achievable in the proposed turbo-coded FTN-IM scheme.

In this paper, we propose a precoded faster-than-Nyquist (FTN) signaling technique for time-domain single-carrier index modulated (IM) symbol transmission. More precisely, eigenvalue decomposition precoding is adopted for the FTN transmission of data bits modulated by single-carrier time-domain IM. While the FTN scheme increases the spectral efficiency and data rate by packing more transmit symbols per block duration than those defined in the Nyquist criterion, time-domain IM works towards the same objective while maintaining symbol sparsity. We analytically derive the constrained capacity of the proposed system. Our simulation results show that the proposed scheme has better bit error ratio (BER) performance over the conventional FTN-IM scheme, particularly for the scenario of a higher packing ratio. In the proposed scheme, 2.5-dB performance gain is observed at the BER of = 10−4, employing the packing ratio of 0.7 and the roll-off factor of 0.5 in a channel-uncoded scenario.

Typical construction of CRC concatenated polar codes append the CRC bits at the end of information bits and then feeds the resulting vector as input to the polar encoder. This construction comes with a caveat that CRC check cannot be performed till all information bits are decoded by the polar decoder. Hence it becomes impossible to do an early termination (ET) of successive cancellation decoder in the case of decoding failure, thereby causing latency and unnecessary power consumption associated with the decoding of bits that follow the first error bit. While interleaving of CRC codeword prior to polar encoding can make ET possible, but it can potentially jeopardize the undetected error rate (UER) of the code. In this paper, a novel construction of interleaved-CRC assisted polar codes is proposed aimed at high ET gain while controlling the rise in UER. Exemplary simulation results are provided.

Puncturing and shortening are widely used methods employed to design arbitrary rate codes from a mother code of given rate. In the context of polar codes, the encoding process has to be completely redone based on the codelength and coding rate for any given shortening/puncturing pattern which makes the implementation of a rate-compatible polar code system very complex. This happens as reliability ordering of the polarized bit-channels gets altered post shortening/puncturing; thus making it necessary to recompute the bit-channel reliabilities tailored to the new reduced codelength followed by sorting them again (in other words, a complete reconstruction). It has been noted before that a bit reversal shortening (BRS) scheme has a special property: it does not require the said reordering of bit-channels, which makes the encoder implementation significantly simple and pragmatic. While this property is extremely intriguing both theoretically and practically, no detailed study on this subject is available in literature. In this paper, we show the relation of BRS with prior art, highlight the said property across wide range of code parameters and then delve deep into what leads up to that property. We observe that like all other schemes, BRS also changes the reliability order of indices, but in a very localized manner. Consequently, the non-frozen set for bit-reverse shortened polar code is nearly same as that of the mother code. Extensive simulation of polar codes is provided to validate the findings.

Wi-Fi Peer to Peer (P2P), commercially known as Wi-Fi Direct, is a recent industry standard that allows user devices to communicate with each other without requiring a Wi-Fi access point or Internet connectivity. Offering promising solutions for secure and high-throughput device to device communication over moderately high range, Wi-Fi P2P can potentially revolutionize M2M communication and Internet of Things (IoT) towards an all-connected wireless ecosystem. Secure Digital (SD) memory cards with built-in processing unit and Wireless LAN chipset can serve as a small standalone communication terminal which on installation of a communication protocol stack and a data-sharing application may enable connection establishment and data communication between memory cards. Such architecture may find interesting applications with manifold advantages for device-to-device data sharing in public gatherings without requiring cellular network or WLAN access points. In this paper, we develop an architecture to establish Wi-Fi P2P connection between SD memory cards and enable automatic data sharing by proximity-based device-to-device communication between mobile user equipments. The prototype does not use any of the resources of host device barring power. The key contribution of this paper is the development of a standalone prototype of our proposition on off-the-shelf WLAN SD memory cards and its experimental performance evaluation.

Content sharing in Delay Tolerant Networks is largely contingent on the cooperation of participating nodes as message dissemination is executed in a store-carry-forward approach. The scope of the term cooperation has largely been limited to content forwarding in prior work. This work considers a universe of distributed content- sources that generate disjoint contents. A population of users who are capable of moving from one source to another are interested only in some selected subset of the localized contents. Interest of users is assumed to vary from one another; being rational entities, they are solely interested in collecting their preferred content(s) at the expense of minimum cost. With solutions like Direct Reciprocity been proposed earlier to force a user to be altruistic in message forwarding, our work starts in this backdrop where preference-based content caching and deletion strategy comes into play even if a user is forced to share her contents with all other encountered users. Alongside, we introduce mobility as a user strategy to characterize the non-cooperation of a user along with deletion of non-preferred cached contents. Under this premise, we explore the optimal strategies that a user can exercise to maximize her benefit corresponding to the strategies adopted by other users. More specifically, we investigate the joint impact of user's mobility and caching strategy on self and overall network performance using a Public Goods game in the Social Dilemma framework evincing the condition when non-cooperation is costlier than cooperation.

The design of an efficient Medium Access Control (MAC) protocol for multichannel ad hoc Cognitive Radio Networks is an important problem and has been the topic of extensive recent research. In this paper, we present the design and performance evaluation of a protocol, Group MAC (GMAC), which is customized for a situation that commonly arises in ad hoc networks: the network consists of multiple groups of nodes such that a large fraction of the traffic of each node needs to be sent to other nodes of its own group. Some examples are: (a) units (e.g., platoons) in a military ad hoc network, (b) divisions in an emergency or disaster relief network, (c) departments in a corporate or university network. Our protocol requires each secondary node to have only one narrowband transceiver, does not rely on a control channel and incorporates a novel technique for dynamically balancing the traffic load of secondary nodes across the set of free channels. We analyze the stability region of the protocol using a queuing theoretic framework. Our extensive simulations show that a large fraction of the bandwidth unoccupied by primary users is utilized by the GMAC protocol for data transmissions.

WiFi Peer to Peer (P2P) aka WiFi Direct enables devices to communicate with each other in a peer to peer manner without requiring any Access Point at typical WiFi speed with WPA2 security. With its huge prospect in revolutionizing device to device communication, WiFi P2P can potentially play a much larger role amid the growing interest in M2M communication and Internet of Things. However, unlike a conventional P2P network which operates on mesh topology, WiFi P2P requires one of its group members to act as Group Owner, with whom all the other devices in the group stay associated. The group suffers from a temporary network disruption when the Group Owner suddenly leaves the group without any prior notice. In addition, restoration of the group connectivity consumes much time which is intolerable for most delay sensitive applications. In this paper, we address this issue using our proposed concept of Seamless Group Reformation which helps in maintaining near continuous connectivity and alleviates over dependence of the group on the Group Owner. The concept is seconded by the proposed mechanism of Dormant Backend Links to cut down the total group-disruption time. We implement the mechanism of Dormant Backend Links on a practical WiFi P2P testbed and present an experimental evaluation.