Spectrum Sharing Scheme Between Cellular Users and Ad-hoc Device-to-Device Users (1301.6980v2)

Abstract: In an attempt to utilize spectrum resources more efficiently, protocols sharing licensed spectrum with unlicensed users are receiving increased attention. From the perspective of cellular networks, spectrum underutilization makes spatial reuse a feasible complement to existing standards. Interference management is a major component in designing these schemes as it is critical that licensed users maintain their expected quality of service. We develop a distributed dynamic spectrum protocol in which ad-hoc device-to-device users opportunistically access the spectrum actively in use by cellular users. First, channel gain estimates are used to set feasible transmit powers for device-to-device users that keeps the interference they cause within the allowed interference temperature. Then network information is distributed by route discovery packets in a random access manner to help establish either a single-hop or multi-hop route between two device-to-device users. We show that network information in the discovery packet can decrease the failure rate of the route discovery and reduce the number of necessary transmissions to find a route. Using the found route, we show that two device-to-device users can communicate with a low probability of outage while only minimally affecting the cellular network, and can achieve significant power savings when communicating directly with each other instead of utilizing the cellular base station.

• The paper introduces a distributed dynamic spectrum protocol that enables D2D communication while controlling interference for cellular users.
• It proposes a novel power control mechanism combined with enhanced route discovery to optimize D2D links and minimize transmission needs.
• Simulations and analytical models demonstrate improved D2D performance and reduced outage probabilities with minimal impact on cellular services.

Spectrum Sharing Scheme Between Cellular Users and Ad-hoc Device-to-Device Users

This paper, authored by Brett Kaufman, Jorma Lilleberg, and Behnaam Aazhang, presents a rigorous exploration of a protocol for enabling ad-hoc Device-to-Device (D2D) communication within the same frequency spectrum as licensed cellular users. The introduction of opportunistic spectrum-sharing methods is grounded in the need for more efficient utilization of available frequency resources, which is crucial as the number of wireless users increases. This research explores the complexities of managing interference to ensure that the quality of service for licensed users remains uncompromised.

Key Contributions

1. Distributed Dynamic Spectrum Protocol: The paper develops a distributed dynamic spectrum protocol allowing D2D users to opportunistically access spectrum used by cellular networks. This protocol is designed to control the interference caused by D2D communications, maintaining it within the allowed interference temperature for cellular users.
2. Power Control and Route Discovery: The authors propose a novel technique for power management that utilizes channel gain estimates to set feasible transmit powers for D2D communication. A two-step protocol is outlined: initially adjusting transmit powers based on interference constraints, followed by route discovery using enhanced dynamic source routing (DSR). The route discovery incorporates network information in discovery packets, which improves route success rates and reduces the number of necessary transmissions.
3. Analytical Framework: The paper provides an analytical expression for the probability of outage for a link between two D2D devices. This analytical development is complemented by simulation results that demonstrate reduced failure rates and significant power savings when employing direct D2D links instead of relying on the cellular infrastructure.
4. Performance Evaluation: Through simulations, the research assesses both the D2D and macro user outage probabilities under the proposed protocol. The results underscore a substantial improvement in D2D link performance, with minimal adverse effects on cellular users.

Practical Implications and Theoretical Contributions

The practical implications of this spectrum-sharing scheme are profound, especially in contexts where high-density areas demand efficient communication solutions without requiring additional infrastructure investment. The ability to utilize statistical estimates for channel gain empowers D2D users to enact their power control, which is critical in maintaining network integrity while optimizing D2D throughput. The work paves the way for enhancing network capacity by dynamically integrating ad-hoc communication capabilities within existing cellular frameworks.

From a theoretical standpoint, the analytical models of interference and power control presented establish a groundwork for future explorations into dynamic spectrum sharing. The nuanced consideration of various pathloss exponents and the impact on outage probabilities provides a comprehensive understanding of the environmental factors affecting signal transmission in shared spectrum scenarios.

Future Developments and Considerations

While the research showcases significant advancements, the potential for further optimization remains. Future work could integrate more advanced channel estimation techniques and explore adaptive power control mechanisms to enhance the robustness of D2D communications further. Additionally, the paper of multiple D2D cluster interactions and the cumulative effect on cellular network performance offers an intriguing direction for continuing this research.

In conclusion, this paper substantially contributes to the body of knowledge in spectrum sharing by offering a practical protocol that balances the needs of licensed cellular networks with those of unlicensed D2D users. The insights gleaned from this work are expected to influence both future research endeavors and practical implementations in network management and optimization strategies.