9 research outputs found
Effective Capacity of Cognitive Radio Links: Accessing Primary Feedback Erroneously
We study the performance of a cognitive system modeled by one secondary and
one primary link and operating under statistical quality of service (QoS) delay
constraints. We analyze the effective capacity (EC) to quantify the secondary
user (SU) performance under delay constraints. The SU intends to maximize the
benefit of the feedback messages on the primary link to reduce SU interference
for primary user (PU) and makes opportunistic use of the channel to transmit
his packets. We assume that SU has erroneous access to feedback information of
PU. We propose a three power level scheme and study the tradeoff between
degradation in EC of SU and reliability of PU defined as the success rate of
the transmitted packets. Our analysis shows that increase in error in feedback
access causes more interference to PU and packet success rate decreases
correspondingly.Comment: Accepted for publication in International Symposium on Wireless
Communication Systems (ISWCS) 201
On the Effective Capacity of IRS-assisted wireless communication
We consider futuristic, intelligent reflecting surfaces (IRS)-aided
communication between a base station (BS) and a user equipment (UE) for two
distinct scenarios: a single-input, single-output (SISO) system whereby the BS
has a single antenna, and a multi-input, single-output (MISO) system whereby
the BS has multiple antennas. For the considered IRS-assisted downlink, we
compute the effective capacity (EC), which is a quantitative measure of the
statistical quality-of-service (QoS) offered by a communication system
experiencing random fading. For our analysis, we consider the two widely-known
assumptions on channel state information (CSI) -- i.e., perfect CSI and no CSI,
at the BS. Thereafter, we first derive the distribution of the signal-to-noise
ratio (SNR) for both SISO and MISO scenarios, and subsequently derive
closed-form expressions for the EC under perfect CSI and no CSI cases, for both
SISO and MISO scenarios. Furthermore, for the SISO and MISO systems with no
CSI, it turns out that the EC could be maximized further by searching for an
optimal transmission rate , which is computed by exploiting the iterative
gradient-descent method. We provide extensive simulation results which
investigate the impact of the various system parameters, e.g., QoS exponent,
power budget, number of transmit antennas at the BS, number of reflective
elements at the IRS etc., on the EC of the system
Effective Capacity Of Delay-Constrained Cognitive Radio Links Exploiting Primary Feedback
In this paper, we study the effective capacity (EC) of cognitive radio (CR) networks operating under statistical quality-of-service (QoS) constraints in an attempt to support real-time applications at the secondary users (SUs). In particular, we analyze the performance gains, in terms of EC and average transmitted power, attributed to leveraging the primary user (PU) feedback overheard at the SU, at no additional complexity or hardware cost. We characterize the EC performance improvement for the SU, in the presence of a feedback-based sensing scheme, under the signal-to-interference-plus-noise ratio (SINR) interference and collision models. Toward this objective, we develop a Markov chain model for feedback-based sensing to compare the performance of a two-link network, a single secondary link, and a primary network abstracted to a single primary link, with and without primary-feedback exploitation. We prove that exploiting the primary feedback at the secondary transmitter improves the EC of the SU under the SINR interference model. On the other hand, interestingly, exploiting the PU feedback messages does not enhance the EC of the SU under the collision model. Nevertheless, exploiting the PU feedback reduces the SU average transmitted power under the two aforementioned models. Finally, we present numerical results, for plausible scenarios, that support our analytical findings