Abstract
Long term evolution advanced (LTE-A) has emerged as a promising mobile broadband access technology aiming to cope with the increasing traffic demand in wireless networks. However, the enhanced spectral efficiency offered by LTE-A may become futile without a better management of scarce and overcrowded electromagnetic spectrum. In this sense, cognitive radio (CR) has been proposed as a potential solution to the problem of spectrum scarcity. Among all the mechanisms provided by CR, opportunistic spectrum access (OSA) aims at a dynamic and seamless use of certain licensed bands provided the licensee is not harmfully affected. This operation requires spectral awareness in order to avoid interferences with licensed systems. In spite of implementing some spectrum sensing mechanisms, LTE-A technology lacks other tools that are needed in order to improve the knowledge of the radio environment. This work studies the adoption of a Geo-located data base (Geo-DB) that cooperatively retrieves and maintains information regarding the location of unutilized portions of spectrum potentially available for OSA. Moreover, the potential benefit of this LTE-compliant OSA solution is evaluated using a calibrated simulation tool, by which numerical results allow us to optimally configure the system and show that the proposed opportunistic system is able to significantly improve its performance.
Highlights
Long term evolution (LTE) was designed to improve mobile broadband, supporting higher-rate services [1]
We introduce a new node in the LTE-A network referred to as the cognitive resource manager (CRM), which coordinates the opportunistic spectrum access (OSA) to the unlicensed spectrum based on the notifications reporting the channel status perceived by the cognitive UEs
Following the weighted cooperative spectrum sensing described in [20], instead of weighting the measured primary signal-to-noise ratio (SNR), we propose to weight the event notifications according to the time when the measurements were triggered and the coherence of the measurements taken inside the same timing advance (TA) range
Summary
Long term evolution (LTE) was designed to improve mobile broadband, supporting higher-rate services [1]. In case that CCs are discontinuous, and assuming that mobile devices only have a single radio interface, once the opportunistic user reads the control channel and finds out its allocated resources the handset has to tune its working frequency to the allocated CC, synchronize to the LTE system to start data transmission or reception and, after a specific time interval, re-tune the radio to the licensed LTE band and read the control channel again This situation is impractical in the ambit of OSA since the required time between re-tunes must be very short in order to provide updated information of the opportunistic resources availability and, even if the handset is able to perform fast re-tuning, there is no useful time left to exploit those frequencies. In [40], an efficient implementation of a Non-Contiguous OFDMA (NC-OFDMA) transceiver is presented for CR applications
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