Abstract
Orthogonal Frequency-Division Multiplexing with Random multiple access (OFDRMA) is discussed for uplink communications, whereby several active users send information towards a single ...base-station (BS), while all other users are dormant. Originally, uplink communication methods included sharing the frequency resources among the active users in an orthogonal fashion, i.e., a central unit is required to dynamically allocate the resources. More recently, non-orthogonal methods have arisen, meaning that several active users share the same frequency bins, but they still do require a central unit to dynamically allocate the resources in a uniform (as possible) manner over the available bandwidth. The task and overhead required for managing the frequency allocations among the users can be quite cumbersome. In OFDRMA, the frequency allocations for any user are independent of the frequency allocations for the other users, and independent of which of the other users are currently active. Rather, OFDRMA relies on random, yet predetermined, allocation of frequency bins for each user, known only to that user and the BS. A multi-user detection approach is presented based on a graphical representation of the system. It is shown to provide robustness against the forced randomness of the scheme. Capacity of OFDRMA and its optimization are analyzed and provided in detail. Simulation results are provided for demonstrating the performance attainable with OFDRMA and the proposed detection scheme. Both the capacity and the simulations are compared with modern multi-user multiple-input multiple-output (MU-MIMO) schemes.
Down-link OFDRMA communications Salomon, Amir J.; Salomon, Benjamin G.; Amrani, Ofer
Wireless networks,
2021/1, Letnik:
27, Številka:
1
Journal Article
Recenzirano
Orthogonal frequency-division multiplexing with random multiple access (OFDRMA) is discussed for down-link communications, whereby a single base-station transmits information towards several active ...users. Current methods for down-link communication partition the frequency resources among the active users in an orthogonal fashion, i.e. a central unit (typically the base-station itself) dynamically allocates the resources such that each user is allocated a fixed and exclusive set of sub-bands (a.k.a.
bins
, or
subcarriers
). The task and overhead required for orchestrating the frequency sub-bands allocations among the users in an optimal fashion can be quite cumbersome, and typically involves increased computational complexity, latency and bandwidth resources. The main purpose we address in this paper is to avoid the task and overhead required in the state-of-the-art OFDM systems in both the base-station and the users, while sacrificing as little as possible in terms of users side error rate performance. This is of particular importance in multi-user multiple-input multiple-output systems, which become increasingly popular these recent years. In OFDRMA a user is assumed to be allocated with a predetermined, randomly selected frequency bins. A multi-antenna multi-user delivery approach is presented based on pre-coding and multi-cast transmission. It is shown to provide robustness against the forced randomness of the scheme. Simulation results are provided for demonstrating the performance attainable with OFDRMA and the proposed transmission scheme.
The paper presents a method for constructing space-time block codes for multiple-input multiple-output channels by concatenating orthogonal designs with the so-called
diversity transform
. Relying on ...unitary transforms, the diversity transform increases the channel alphabet without sacrificing information rate, bandwidth, or Euclidean distance. The distribution of the resulting channel alphabet is shown to quickly become Gaussian-like. Specific code matrices are constructed and optimized based on the cutoff rate. Both optimum and, reduced-complexity, suboptimum detection algorithms are presented. Simulation results are provided for demonstrating the gains attainable when using the proposed codes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This paper concerns the construction of the so-called augmented product codes and augmented product lattices. These are obtained by augmenting product codes or product lattices from certain classes ...thus obtaining higher dimensional codes or lattices from the same class, respectively. Certain properties of the augmented product construction are derived, and specific construction examples are given. In particular, it is shown that the Reed-Muller codes, the Golay code, the Barnes-Wall lattices, as well as the Leech lattice all have various augmented product constructions.
A binary product lattice is generated from two binary component lattices of lower dimensions by employing the Kronecker product. This work focuses on codes carved from binary product lattices. ...Defined as such, an intriguing problem is that of effectively mapping independent data sequences onto a selected subset of lattice points. A novel approach is disclosed yielding an explicit connection between source bits and lattice points. Decoding methods typically used for binary product codes do not apply for product lattices. Several alternative decoding approaches are discussed. In particular, a provably bounded-distance decoder is presented. It relies on the fact that a product lattice code point may be regarded as a two-dimensional array whose rows and columns are points in the component lattices. The obtained results are compared with classical lattices known in the art
Coded modulation scheme of high-coding gain is presented for flat fading channels. The scheme introduces a product construction that employs two types of codes: "standard" good codes and codes that ...are more suitable for the fading environment. Short-blocklength codes of unique features are, thus, obtained for the bandwidth-limited regime. Using this approach, codes of bandwidth efficiencies 1, 2, and 3 bits/s/Hz are detailed. An iterative decoding algorithm for this product construction is devised. It relies on separate columns/rows decoding linked by (reliability) information transfer. Simulation results reveal that these codes compare favorably with known codes of short block-length when perfect channel state information is available to the receiver. The proposed approach is easily extended for the frequency-selective fading channel with multicarrier signaling
Coded modulation scheme of high coding gain is presented for slowly-varying flat fading channels. The scheme introduces a product construction employing two types of codes: "standard" good codes and ...codes that are more suitable for the fading channel. Short-blocklength codes of unique features are thus obtained. Using this approach, codes of bandwidth efficiencies 1,2, and 3 bits/s/Hz are detailed. An iterative decoding algorithm for this product construction is devised. It relies on separate columns/rows decoding linked by (reliability) information transfer. Simulation results reveal that these codes compare favorably with known codes of short block-length.
Space-time coding with increased diversity Salomon, A.J.; Amrani, O.
2008 IEEE 25th Convention of Electrical and Electronics Engineers in Israel,
2008-March
Conference Proceeding
This paper presents a method for constructing space-time block codes for multiple-input multiple-output (MIMO) Rayleigh fading channels. It employs orthogonal designs combined with the so-called ...diversity transform. Orthogonal designs provide the maximum diversity order for a given number of transmit and receive antennas. The diversity transform relies on unitary transforms that increase the channel alphabet; it does not alter the distance between input sequences, nor the bandwidth or information rate. A scheme of high diversity gain is tailored for any antenna array and signal constellation. Simulation results reveal that this scheme attains higher coding gains than other results known in the art.
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