Device-to-Device Communication in 5G Cellular Networks: Challenges, Solutions, and Future Directions

CTN Issue: October 2014 IEEE Communications Magazine

Authors: Mohsen Nader Tehrani (University of Waterloo), Murat Uysal (Özyegin University), and Halim Yanikomeroglu (Carleton University)
Title: “Device-to-Device Communication in 5G Cellular Networks: Challenges, Solutions, and Future Directions”
Publication: May, 2014 IEEE Communications Magazine

While the conventional cellular architecture consists of connections from base stations to user equipment, 5G systems may well rely upon a two-tier architecture consisting of a macrocell tier for base station to device communication, and a second device tier for device to device (D2D) communications.  Such architectures are a hybrid of conventional cellular and ad hoc designs.  The authors first taxonomize possible D2D architectures and outline three technical challenges in D2D, namely, security, interference management, and resource allocation.  Second, the authors describe possible pricing models to incentivize users to let their devices serve as relays for other communications. 

The D2D architecture taxonomy consists of four designs:

  1. Device relaying with operator controlled link establishment (DR-OC)
  2. Direct D2D communication with operator controlled link establishment (DC-OC)
  3. Device relaying with device controlled link establishment (DR-DC)
  4. Direct D2D communication with device controlled link establishment (DC-DC)

Observe the base station (operator) is only involved in the first two designs, and in fact the fourth design is a purely ad hoc connection (i.e., not requiring a cellular network). 

The first technical challenge is security.  The parties sending and receiving the data must be assured their data is not accessible to the relay, and the relay must be assured the data it is handling is benign.  The authors distinguish between closed and open access designs, where the user of a closed access device explicitly allows the device to relay for a specific list of trusted sources.  There is an existing body of research on security issues for D2D designs, including routing, key management, and attack identification.

The second technical challenge is interference management.  D2D designs must carefully manage channels designated exclusively for D2D connections, as well as channels jointly used by both D2D connections and connections with the base station.  The existing literature on D2D interference management addresses channel assignment via game theory, D2D admission control, D2D power control, and D2D relay selection. 

The third technical challenge is resource allocation, and the possible solutions are specific to the D2D design.  Under the DR-OC and DC-OC designs, for example, the base station can (partially) manage the relay and channel selections.  Under the DR-DC and DC-DC designs, however, there is no centralized supervision on either relay selection or channel management.  

Besides the technical challenges, there is the very practical problem of incentivizing users to lend their devices to serve as relays for the traffic of others, especially since these connections will consume bandwidth, storage, and battery power on the relay.  Again, the appropriate class of solutions depends upon the D2D design. 

For DR-OC designs, the operator may incentivize users to lend their devices as D2D relays by offering a bill reduction in proportion to the amount of data relayed that month.  By designing an appropriate utility function for each device based on the bandwidth consumed and the bandwidth relayed, as well as a revenue function for the network operator, the authors demonstrate an incentive compatibility between the operator and the users. 

For DC-OC designs, the challenge is to incentivize users to use D2D communications instead of free WiFi or Bluetooth connections, which can be cast as a spectrum trading problem within the context of auction theory.  The authors discuss various auction mechanisms including the Bertrand game, and present an example to demonstrate the increase in operator revenue.

Finally, for DR-DC and DC-DC designs, the operator is external from the connection, and as such the two parties involved should agree on a pricing scheme (or simply not charge for the relay).  Cited studies demonstrate the performance improvement achievable when altruistic users offer their devices to serve as relays.

References

[Top10, 2014]           IEEE Communications Society, “The July 2014 list of the ten most popular articles published in ComSoc periodicals viewed online, based on PDF views through IEEE Xplore”, Available at http://www.comsoc.org/topten.

[ComMag, Feb. 2014]           IEEE Communications Magazine, “5G Wireless Communications Systems: Prospects and Challenges (Part 1)”, February 2014.

[ComMag, May 2014]           IEEE Communications Magazine, “5G Wireless Communications Systems: Prospects and Challenges (Part 1)”, May 2014.

[JSAC, June 2014]      IEEE Journal on Selected Areas in Communications, “Special Issue on 5G Wireless Communications”, June 2014.

[5GMWI]        IEEE Communications Society Emerging Technical Subcommittee on 5G Mobile Wireless Internet, Available at http://www.comsoc.org/about/committees/emerging.

[5GT&C]         IEEE Communications Society 5G Training and Certification, Available at http://www.ieee-5g.org.

[5GWorkshop]          International Workshop on Emerging Technologies for 5G Wireless Cellular Networks (at IEEE Globecom 2014), December 8, 2014, Available at http://wcsp.eng.usf.edu/5g/2014/.

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