2,277 research outputs found
Mobility Increases the Data Offloading Ratio in D2D Caching Networks
Caching at mobile devices, accompanied by device-to-device (D2D)
communications, is one promising technique to accommodate the exponentially
increasing mobile data traffic. While most previous works ignored user
mobility, there are some recent works taking it into account. However, the
duration of user contact times has been ignored, making it difficult to
explicitly characterize the effect of mobility. In this paper, we adopt the
alternating renewal process to model the duration of both the contact and
inter-contact times, and investigate how the caching performance is affected by
mobility. The data offloading ratio, i.e., the proportion of requested data
that can be delivered via D2D links, is taken as the performance metric. We
first approximate the distribution of the communication time for a given user
by beta distribution through moment matching. With this approximation, an
accurate expression of the data offloading ratio is derived. For the
homogeneous case where the average contact and inter-contact times of different
user pairs are identical, we prove that the data offloading ratio increases
with the user moving speed, assuming that the transmission rate remains the
same. Simulation results are provided to show the accuracy of the approximate
result, and also validate the effect of user mobility.Comment: 6 pages, 5 figures, accepted to IEEE Int. Conf. Commun. (ICC), Paris,
France, May 201
Social Data Offloading in D2D-Enhanced Cellular Networks by Network Formation Games
Recently, cellular networks are severely overloaded by social-based services,
such as YouTube, Facebook and Twitter, in which thousands of clients subscribe
a common content provider (e.g., a popular singer) and download his/her content
updates all the time. Offloading such traffic through complementary networks,
such as a delay tolerant network formed by device-to-device (D2D)
communications between mobile subscribers, is a promising solution to reduce
the cellular burdens. In the existing solutions, mobile users are assumed to be
volunteers who selfishlessly deliver the content to every other user in
proximity while moving. However, practical users are selfish and they will
evaluate their individual payoffs in the D2D sharing process, which may highly
influence the network performance compared to the case of selfishless users. In
this paper, we take user selfishness into consideration and propose a network
formation game to capture the dynamic characteristics of selfish behaviors. In
the proposed game, we provide the utility function of each user and specify the
conditions under which the subscribers are guaranteed to converge to a stable
network. Then, we propose a practical network formation algorithm in which the
users can decide their D2D sharing strategies based on their historical
records. Simulation results show that user selfishness can highly degrade the
efficiency of data offloading, compared with ideal volunteer users. Also, the
decrease caused by user selfishness can be highly affected by the cost ratio
between the cellular transmission and D2D transmission, the access delays, and
mobility patterns
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