This applied research project intends to design or plan fixed/portable and mobile WiMAX (Worldwide Interoperability for Microwave Access) WMANs (Wireless Metropolitan Area Networks), pioneering implemented in Portugal. Besides the benefits of its operation in the context of university, hospital and urban environments it will be very useful for demonstration and research purposes.
The project involves five main tasks:
1-Design and Development of IEEE 802.16 Microwave Links for Fixed/Portable Communications.
2- Planning of a Cellular IEEE802.16e for Mobility Support.
3- Network Architectures for Interoperability and Mobile IP between Wi-Fi and WiMAX networks.
4- Security for IEEE 802.16.
5-Multimedia Service and Applications for Mobile Platforms.
Our methodologies will be based on detailed planning, as well as network implementation, demonstration and validation. Measurements will be performed to evaluate QoS, and help both the dimensioning and the optimization processes.

The objective of the developed point-to-point, PTP, demonstrator was to connect the Health Sciences Faculty of the University of Beira Interior, FCS/UBI, in Covilhã, to the Hospital Amato Lusitano, HAL, in Castelo Branco, and to the Hospital Sousa Martins, HSM, in Guarda. The planning process and the development of a point-to-multipoint, PTM, network that covers the whole district of Covilhã were also addressed. A network of this type is justified by the need of creating an Intranet that allows to efficiently exchanging contents within a context of mobility, and an efficient use of e-learning multimedia platforms.

WiMAX uses OFDM and a kind of dynamic modulation scaling, i.e., the system is able to adapt itself to the best modulation/coding schemes by considering carrier-to-noise-plus-interference versus data rate constraints. In IEEE 802.16-2004, channels of 3.5, 7 and 10 MHz are defined. As link distances of the order of tens kilometres can be guaranteed, WiMAX is as a good solution for broadband backhaul; while offering high data rates, it enables a distance range up to 50 km (in the PTP case), and cell coverage radius between 2 and 5 km (in the PTM case).

Adaptive modulation and coding schemes ensure that a quality signal is delivered over the distance by decreasing throughput thus decreasing the packet loss rate. One of the best characteristics of WiMAX is the ability to support multimedia and IP (Internet Protocol) communications, e.g., videoconference, voice over IP, and communication of high resolution video/image. One example is the possibility of students having access to e-contents while they are at home or moving through the city. Besides, WiMAX PTM networks can support emergency and safety, Firemen and Polices services, hence it is possible to send real time images, e. g., from the accident, or fire scenes.

For the PTP component, the dimensioning of 5.8 GHz WiMAX links was addressed. Field trials were held by using 5.4 GHz pre-WiMAX equipment. It was necessary to verify the existence of line of sight, LoS, between the transmitters for the placement of the repeater previously determined for the WiMAX link between FCS/UBI, Covilhã, and HAL, Castelo Branco, and if there is no obstruction to the first Fresnel ellipsoid. We used the Alvarion BreezeNET B14 in the field trials. It presents the following characteristics: f = 5.4 GHz, b_rf = 20 MHz, G_t = G_r = 21dBi, and P_t = 9 dBm, the maximum output power.

The design of the link with relays had into consideration the carrier to noise ratio, C/N, and the minimum carrier to noise ratio with fading, C/N_{min_fad}. From the dimensioning process, with γ = 2, for the second clause, the three types of modulations (low to high order ones) can be used. Field trials results are similar to the ones extracted from the theoretical model.

The Base Station, BS, and the Customer Premise Equipment are presented in . Field trials are being performed in Covilhã, and results on signal-to-noise ratio, SNR, and throughput were obtained. In these particular field tests, our ODU was operating at 3551.75 and 3451.75 MHz (down- and uplink, respectively). The maximum ODU transmitter power is 28 dBm but its actual value is limited by EIRP_max = 30 dBm. The configuration of the WiMAX QoS classes lead us to promising improvements.