203,974 research outputs found
Gaussian Two-way Relay Channel with Private Information for the Relay
We introduce a generalized two-way relay channel where two sources exchange
information (not necessarily of the same rate) with help from a relay, and each
source additionally sends private information to the relay. We consider the
Gaussian setting where all point-to-point links are Gaussian channels. For this
channel, we consider a two-phase protocol consisting of a multiple access
channel (MAC) phase and a broadcast channel (BC) phase. We propose a general
decode-and-forward (DF) scheme where the MAC phase is related to computation
over MAC, while the BC phase is related to BC with receiver side information.
In the MAC phase, we time share a capacity-achieving code for the MAC and a
superposition code with a lattice code as its component code. We show that the
proposed DF scheme is near optimal for any channel conditions, in that it
achieves rates within half bit of the capacity region of the two-phase
protocol.Comment: 6 pages, 3 figures, accepted for publication in IEEE Transactions on
Communication
Sub-channel Assignment, Power Allocation and User Scheduling for Non-Orthogonal Multiple Access Networks
In this paper, we study the resource allocation and user scheduling problem
for a downlink nonorthogonal multiple access network where the base station
allocates spectrum and power resources to a set of users. We aim to jointly
optimize the sub-channel assignment and power allocation to maximize the
weighted total sum-rate while taking into account user fairness. We formulate
the sub-channel allocation problem as equivalent to a many-to-many two-sided
user-subchannel matching game in which the set of users and sub-channels are
considered as two sets of players pursuing their own interests. We then propose
a matching algorithm which converges to a two-side exchange stable matching
after a limited number of iterations. A joint solution is thus provided to
solve the sub-channel assignment and power allocation problems iteratively.
Simulation results show that the proposed algorithm greatly outperforms the
orthogonal multiple access scheme and a previous non-orthogonal multiple access
scheme.Comment: Accepted as a regular paper by IEEE Transactions on Wireless
Communication
Distributed Algorithms for Learning and Cognitive Medium Access with Logarithmic Regret
The problem of distributed learning and channel access is considered in a
cognitive network with multiple secondary users. The availability statistics of
the channels are initially unknown to the secondary users and are estimated
using sensing decisions. There is no explicit information exchange or prior
agreement among the secondary users. We propose policies for distributed
learning and access which achieve order-optimal cognitive system throughput
(number of successful secondary transmissions) under self play, i.e., when
implemented at all the secondary users. Equivalently, our policies minimize the
regret in distributed learning and access. We first consider the scenario when
the number of secondary users is known to the policy, and prove that the total
regret is logarithmic in the number of transmission slots. Our distributed
learning and access policy achieves order-optimal regret by comparing to an
asymptotic lower bound for regret under any uniformly-good learning and access
policy. We then consider the case when the number of secondary users is fixed
but unknown, and is estimated through feedback. We propose a policy in this
scenario whose asymptotic sum regret which grows slightly faster than
logarithmic in the number of transmission slots.Comment: Submitted to IEEE JSAC on Advances in Cognitive Radio Networking and
Communications, Dec. 2009, Revised May 201
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