The throughput-delay trade-off problem for cooperative spectrum sensing (CSS) is investigated. It is proved that the maximum achievable throughput and the minimum transmission delay cannot be obtained simultaneously. An efficient algorithm is proposed to optimize the sensing bandwidth and the final decision threshold jointly such that the throughput is maximized while the delay is constrained. It is demonstrated that convex optimization plays an essential role in solving the problem in an efficient way. Simulation results show that the proposed optimal scheme can significantly improve the throughput of the secondary users (SUs) under the constraint that the delay Quality of Service (QoS) requirements of the SUs are satisfied.

Cognitive radio (CR) is a potential technology to improve the spectrum efficiency by allowing the secondary users to temporarily utilize the unused licensed spectrum of the primary users (PUs) [

In the frame structure of CSS [

In this paper, we study the throughput-delay trade-off problem for CSS with the new frame structure. It is proved that the maximum throughput and the minimum transmission delay cannot be obtained simultaneously. Our object is to design the sensing parameters to maximize the throughput of the SUs under the constraint that the delay QoS requirements of the SUs are satisfied.

We focus on optimizing the sensing bandwidth and the final decision threshold jointly such that the throughput is maximized while the delay is constrained. An efficient algorithm is proposed to obtain the optimal scheme. It is demonstrated that convex optimization plays an essential role in solving the associated design problems. Simulation results show that different delay QoS requirements require different values of sensing bandwidth. The throughput of the SUs can be greatly improved by using the proposed optimal scheme.

The rest of this paper is organized as follows. In Section

In CSS, consider the case that the SUs know the PU transmission bandwidth

New frame structure for CSS.

Considering that energy detection is employed to detect the status of PU in the local sensing step, the false alarm and detection probabilities at each SU are [

Suppose that the counting rule is employed in FC; then, the final false alarm and detection probabilities are [

There are two possible scenarios for which the SU can transmit its data. Scenario 1: the PU is correctly detected to be absent. The probability of scenario 1 happening is

In the new CSS frame structure, the SU transmission delay occurs in two cases: false alarm and correct detection of PU [

To guarantee the QoS of the SUs, maximizing the throughput of the SUs

For a given

Hence,

In scenario 2, the CR network experiences interference from the PU; obviously,

In this section, we will investigate the throughput-delay trade-off problem from a convex optimization perspective. Let

Substituting (

Taking the first derivative of

Taking the first derivative of

We know that

Illustration of the curves:

From the above analysis, we can conclude that

Different SUs have different QoS requirements. Let

Illustration of the curves: normalized throughput

For each

According to

Calculate and compare

To evaluate the throughput-delay trade-off for various sensing schemes, simulation results have been conducted in this section. The frame duration is

Figure

Normalized throughput

In Figure

Normalized throughput

In Figures

Normalized throughput

Normalized throughput

This paper studies the new CSS frame structure and formulates the throughput-delay trade-off problem. Particularly, we optimize the sensing bandwidth and the final decision threshold jointly to maximize the throughput of the SUs under the constraint that the delay QoS requirements of the SUs are satisfied. And we have demonstrated the key role of convex optimization in solving the associated design problems. Simulation results have shown that different delay QoS requirements require different optimal

According to (

According to [

Therefore,

The authors declare that there is no conflict of interests regarding the publication of this paper.

This work is supported by the National Basic Research Program of China (973 no. 2009CB3020400) and the Jiangsu Province Natural Science Foundation under Grant BK2011002.