In this paper we present an original way to simplify the architecture of a frequency synthesizer for the 3.1-10.6 GHz band. On the basis of measurement results, obtained by a produced CMOS prototype, the architecture performances are analyzed. As spur frequencies are inevitably generated, we propose to apply an interferences reduction method at the receiver. This solution allows meeting the MultiBand OFDM (Orthogonal Frequency Division Multiplexing) requirements, despite the imperfect spectrum of the generated frequencies and allows simplifying the synthesizer's structure, limiting the use of band-pass filters.

This paper introduces flexible radio techniques inside integrated circuits in order to tackle the interconnect issue for many-core chips. We propose to take benefits from OFDMA for a RF-interconnect associated to a carrier allocation policy and adaptive modulation. A 20 GHz bandwidth is shared between 32 tile sets made of 32 tiles of 4 cores each, for a 4096 cores chip. We adopt a cognitive radio approach in order to dynamically share 1024 carriers, which avoids inter-cluster communication contention and decreases latency compared to conventional static approaches.

A paradigm shift is apparent in Chip Multiprocessor (CMP) design, as the new performance bottleneck is becoming communication rather than computation. It is widely provisioned that number of cores on a single chip will reach thousands in a decade. Thus, new high rate interconnects such as optical or RF have been proposed by various researchers. However, these interconnect structures fail to provide essential requirements of heterogeneous on-chip traffic; bandwidth reconfigurability and broadcast support with a low complex design. In this paper we investigate the feasibility of a new Orthogonal Frequency Division Multiple Access (OFDMA) RF interconnect for the first time to the best of our knowledge. In addition we provide a novel dynamic bandwidth arbitration and modulation order selection policy, that is designed regarding the bimodal on-chip packets. The proposed approach decreases the average latency up to 3.5 times compared to conventional static approach.

In OFDMA, the total available subcarriers are assigned to different users for simultaneous transmission. In case of an unsynchronized uplink OFDMA, each user has a different carrier frequency offset (CFO), which results in loss of orthogonality among subcarriers and causes severe intercarrier interference. In this paper, a self- successive interference canceller (self-SIC) algorithm is proposed for uplink OFDMA systems to mitigate both the self-intercarrier interference and multiuser interference resulting from carrier frequency offsets. We show that for a carrier allocation with larger blocksizes, the proposed compensation algorithm significantly reduces the implementation complexity without performance degradation.

In this paper, we investigate the effect of subcarrier allocation on the CFO for uplink OFDMA systems. Carriers are allocated to the users in order to get maximum throughput by making use of the channel frequency diversity. But in systems with CFO, while allocating the carriers to the users, attention must be paid to the ICI resulting due to CFO. In this paper we propose a carrier allocation scheme that provides a good compromise between the throughput maximization and robustness to the CFO induced ICI for systems with and without channel state information (CSI).

In this paper, we propose a joint estimation method of carrier frequency offsets (CFO) and channel impulse responses (CIR) for an uplink OFDMA system. We consider the CFOs come into play from the emitters due to frequency mismatch between the terminals and base station oscillators. We also take into account the cyclic prefix to derive a new model of the received signal.

Orthogonal Frequency Division Multiplexing (OFDM) is very sensitive to carrier frequency offsets (CFO). The CFO results in intercarrier interference (ICI). This drawback of OFDM is inherited to Orthogonal Frequency Division Multiple Access (OFDMA). In this paper, we propose a new ICI model for an uplink OFDMA system that takes into account the presence of the cyclic prefix which is usually ignored. Simulations validate the accuracy of our derivation. The subcarrier allocation is revisited in the presence of CFO.

Direct-conversion architectures suffer from the mismatch between the in-phase (I) and the quadrature-phase (Q) branches, commonly called I/Q imbalance. Even low I/Q imbalances imply poor performance of orthogonal frequency division multiplexing (OFDM) systems. In this paper, we propose a new algorithm that uses both training and data symbols in a decision-directed fashion to jointly estimate the channel and compensate for high receiver I/Q imbalance. Simulation results show that our method can compensate for high I/Q imbalance values and also estimate a frequency selective channel.

This paper presents the impact of the high-frequency memory of a non-linear amplifier on a multi-carrier (OFDM) transmission and an original, yet very simple, method to compensate for it directly at the transmitter. Our method is efficient thanks to the usage of a long enough cyclic prefix, as in actual OFDM systems.