Channel capacity of a cognitive radio network in GSM uplink band

Abstract

Cognitive radio technology enables the reuse of locally vacant frequency bands for better spectrum utilization and improved overall bandwidth efficiency. In this paper we analyze the practical capacity limits achievable by the (unlicensed) secondary users (SU) sharing bandwidth with (licensed) primary users in 850 MHz GSM uplink frequency band. The achievable capacity limits per user are compared under different constraints and interference scenarios. In order to minimize the impact on PU, we limit the instantaneous interference power from SU to PU in all cases of the investigation. The results show that the additional limit on the SU transmit power to 27 dBm results in a 10% drop in channel capacity, whereas treating PU interference as additive Gaussian noise results in a 50% capacity drop. The effects on the capacity by PU channel occupancy, location of secondary user cell, and log-normal fading spread are also studied. Results show that the average channel capacity is rather insensitive to secondary cell locations. A significant capacity gain can be achieved when PU channel occupancy drops from 50% to 10% or the standard deviation of log normal fading decreases from 8 to 4 dB.

RF-spectrum opportunities for cognitive radio networks operating over GSM channels

“…Recently, the work in [3] evaluated the possibility of using GSM whitespaces in rural areas for dynamic spectrum sharing, therefore supporting the growth of community cellular networks, and consequently, improving the rural access to communications services. Gao et al [4] analyze the practical capacity limits that can be achieved by an opportunistic network when using the 850 MHz GSM uplink frequency. The capacity limits were evaluated under different constraints such as the instantaneous interference power limit to the GSM basestation and the SU transmit power limit.…”

Radar, TV and Cellular Bands: Which Spectrum Access Techniques for Which Bands?

“…Despite the large number of customers, studies reveal that cellular systems' spectrum occupancy is low in rural areas and during night time periods [16]. The studies in [11], [12], [16] also point out the underutilization of cellular uplink bands as a result of Internet traffic asymmetry and the base station's higher transmit powers and continuous transmission on the logical channels in the DL band.…”

“…-GSM -The required thresholds were measured for a macro-BS receiver and mobile station with a sensitivity of -114 dBm and -102 dBm, respectively, and a minimum carrier to interference ratio (CIR) of 9 dB before service degradation [11]. -UMTS -In [12], the authors estimated that a 1 dB increase in the noise floor at the UMTS receivers causes a negligible degradation in the capacity and coverage of UMTS cells.…”

“…Looking at the literature that goes beyond this particular scenario, we highlight the articles on PU exclusion zone size estimation [11]- [14], the spectrum occupancy measurement campaigns [15], [16], and the EU FP7 QUASAR project [17]- [20]. In these studies, the economic value for opportunistic use of several licensed bands is assessed, based on their occupancy and on the main characteristics of their incumbents.…”

Capacity of Hybrid Cognitive Radio Networks With Distributed VAAs

“…2 shows the normalized ergodic link capacity of a virtual MIMO link C L given by (9) as a function of ρ bs with different values of ρ cr and M t . The normalized ergodic link capacitiesC L of real MIMO systems given by (12) are also shown for comparisons. Clearly, with the increase of M t , both the real and virtual MIMO channel capacities increase.…”