Walid A. Hassan

A survey of cognitive radio and TV white spaces in Malaysia

Cognitive radio CR enables spectrum sharing by allowing new unlicensed services from secondary users to operate in pre-allocated bands in an opportunistic manner. TV white space TVWS is a portion of the spectrum in ultra-high frequency UHF and very-high frequency bands, which is not utilised by primary users in specific time and location. It is envisaged that more spectrum will be available after digital switchover DSO TV transmission replaces the current analogue system. Recently, the regulators in the USA and in the UK have given approval for companies to operate new communication systems with the capability of utilising TVWS spectrum. This paper provides a comprehensive overview of the CR technology and quantifies the TVWS status in Malaysia to expose the spectrum reuse opportunities for future secondary user deployment. Taking the 18 major cities in Malaysia into consideration, we find that all seven TV stations utilise from two to seven of the UHF channels. In our analysis, three usage scenarios were considered, where the utilisation of the 40 UHF channels is full, half and a third. For each case, it was discovered that TVWS was 82.5%, 65% and 46.1%, which can be opportunistically utilised by CR users. Copyright

Studying different propagation models for LTE-A system

This paper investigates the different empirical propagation models for the next mobile generation known as the Long Term Evolution - Advanced (LTE-A) in the 2GHz band.. The effects of the propagation models are analyzed in urban, suburban and rural environments by using Monte-Carlo statistical methodology. The Joint Task Group 5-6 (JTG5-6) propagation model is discussed in the paper along with the free Space, Extended Hata and the ITU-R P.1546-4. The results show that the Extended Hata model is feasible for LTE-A system to compute the path loss when deployed in different environments.

Spectrum Sharing Method for Cognitive Radio in TV White Spaces: Enhancing Spectrum Sensing and Geolocation Database

This paper proposes a system called Wireless Link based on Global Communication Channel (WLGCC) to enhance the spectrum sharing between digital broadcasting (DB) services and the cognitive radio (CR) system in the licensed band of 470?790 ㎒. The WLGCC aims to enhance the spectrum sensing and geolocation database (GLD) spectrum sharing methods in the CR system. Spectrum sensing can be enhanced by receiving the status of the used frequencies from the WLGCC, thereby eliminating the need for a low detection threshold (i.e., avoiding the hidden node problem). In addition, the GLD can be enhanced by providing a reliable communication link between the database and the CR device in the form of an unused TV white space that is reserved as the proposed Global Communication Channel (GCC). This paper analyzes the coexistence of the new WLGCC system and the DB service in terms of avoiding additional interference. Specifically, we mathematically determine the WLGCC parameters, such as the in-band and out-of-band power levels, and operation coverage, and verify them using Monte Carlo simulation. The results show that WLGCC does not degrade the existing DB service and reliably transmits information of the vacant (or used) frequency bands to the CR.

A Spectrum Sharing Model for Compatibility between IMT-Advanced and Digital Broadcasting

Recently, the International Telecommunication Union allocated the 470?862 MHz band to the digital broadcasting (DB) service. Moreover, the 790?862 MHz sub-band will be allocated to the next-generation mobile system, known as the International Mobile Telecommunication ? Advanced (IMT-A), and to the DB on a co-primary basis in the year 2015. Currently, two candidate technologies are available to represent the IMT-A system; the Mobile WiMAX and Long Term Evolution ? Advanced (LTE-A). One of the main criteria of the IMT-A candidate is to not cause additional interference to the primary service (i.e., DB). In this paper, we address the spectrum sharing issue between the IMT-A candidates and the DB service. More precisely, we investigate the interference effect between the DB service and the mobile network, which could be either LTE-A or WiMAX. Our study proposes a spectrum sharing model to take into account the impact of interference and evaluates the spectrum sharing requirements such as frequency separation and separation distance. This model considers three spectrum sharing scenarios: co-channel, zero guard band, and adjacent channel. A statistical analysis is performed, by considering the interferer spectrum emission mask and victim receiver blocking techniques. The interference-to-noise ratio is used as an essential spectrum sharing criterion between the systems. The model considers the random distribution of the users, antenna heights, and the bandwidth effect as well as the deployment environment in order to achieve spectrum sharing. The results show that LTE-A is preferable to WiMAX in terms of having less interference impact on DB; this can eventually allow the operation of both services without performance degradation and thus will lead to efficient utilization of the radio spectrum.

The Feasibility of Coexistence Between 5G and Existing Services in the IMT-2020 Candidate Bands in Malaysia

In 2015, the international telecommunication union (ITU) proposed 11 candidate millimeter-wave bands between 24 and 86 GHz for the deployment of future fifth mobile generation (5G) broadband systems. Furthermore, the ITU called for spectrum-sharing studies in these bands. Since 5G specifications are not yet defined, the utilization of radio spectrum by 5G mobile systems will assist in identifying these specifications. This paper introduces Malaysia as a case study for the deployment of 5G systems. This includes a discussion of the current status of the Malaysian telecommunication market. Then, we investigate the current services that are already deployed in the proposed bands. Our investigation shows that the fixed (F) service is the most deployed as a primary service in the candidate bands. For this reason, a preliminary spectrum-sharing study is conducted on the basis of a modified 5G spectrum-sharing model to evaluate the feasibility of coexistence between 5G and F services in the 28-GHz band. Our modified methodology can be used for spectrum-sharing studies between 5G and any other services for an initial spectrum-sharing investigation. The results show that the F service will be severely affected by the 5G system transition in the 28-GHz band, especially in the base station (BS)-to-BS sharing scenario. The best band from the perspective of current spectrum allocation for 5G systems is the 45-GHz (i.e., 45.5–47 GHz) band, since it is already reserved for mobile service for primary allocation and not utilized. This paper is carried out concurrently with current worldwide efforts investigating spectrum sharing, as requested by the ITU in agenda item 1.13 for the next world radio conference 2019.

Compatibility between the IMT-a service with digital broadcasting in the digital dividend band

One of the outcomes in the last world radio communication conference 2007 (WRC-07) is assigning the 790-862 MHz band to the digital broadcasting (DB), and the new mobile system called International Mobile Telecommunication - Advanced (IMT-A) in co-primary basis in 2015. Until that year, the primary service (i.e., DB) should be protected from the new system (i.e., IMT-A). This paper investigates the spectrum sharing requirements such as separation distance and the frequency separation between DB and IMT-A in the 790-862 MHz band. Our study utilizes the Interfere Spectrum Emission Mask (ISEM) and the victim receiver blocking (VRB) as spectrum sharing models based on the Interference-to-Noise ratio (INR) if -6dB as a spectrum sharing criterion. The results show that high interference impact occurs in rural area deployments, whereas, the coexistence could be achieved in urban areas, requiring less separation distance. (4 pages)

Optimizing the coexistence between HAPS platform and terrestrial system in 5.8GHz band

The 5850-7075MHz band is profoundly utilized for the fixed service such as Terrestrial Systems (TS) and microwave access (WiMAX) in various parts of the world. Nowadays, the High Altitude Platform System (HAPS) became a recognized system in this band. Therefore, terrestrial links are one of the most considerable interference with the HAPS gateway (HAPSGS) links. Hence, the legitimated interference level between HAPS and TS must be investigated to prevent performance degradation to both systems. This paper investigates the compatibility between HAPS and TS for microwave access (WiMAX) when both systems operate in co channel sharing scenario. This is done by evaluating the downlink (DL) and uplink (UL) performance of both systems. The compatibility results are based on the theoretical derivation of spectrum sharing scenario between HAPS and Terrestrial WiMAX user (TS) located in the coverage area of HAPS in high rain attenuation areas by using the deterministic methodology. This assessment has been executed in the urban area elevation angle. The performance of the system is evaluated in terms of interference to noise ratio (INR) of TS receiver inside the urban area coverage (UAC) of HAPS. Based on the study results, the minimum separation distance should be between 15 to 18 kilometers away from the reference point (i.e. Nadir Point (NP)). The isolation technique is applied in the distances less than 15 km and above 18 km in order to mitigate the interference. Consequently, the maximum isolation values should be 30.92 dB and 13.4 dB inserted between the FS and HAPS Gate Station (HAPSGS) and HAPS airship (HAPSAS) respectively to prevent the co-channel interference.