Wimax standards and Security The Wimax

Nonspecified Transmitter Measurements

The ACPR (sometimes also known as adjacent channel leakage ratio, or ACLR) is a measure of the transmitter energy that is leaking into an adjacent or alternate channel [11]. In practice, a very small amount of the transmitter energy will show up in other nearby channels. Aspectrum analyzer can easily make this measurement. First, we can measure the in-channel power within the assigned channel for the DUT. The spectrum analyzer can be retuned to a

frequency offset one channel away and the leakage power is measured. ACPR is the ratio of average power in the adjacent frequency channel to the average power in the assigned channel. The acceptable value for ACPR is from 30 to 80 dB, depending upon the application [11].

The maximum output power for WiMAX applications is generally spec- ified by local regulations, depending upon the band of operation. Higher transmitter output power will cause unnecessary interference in the system. Moreover, for handheld devices excessive output power will cause unnec- essary battery drain. Test equipment such as power meters and spectrum analyzers are ideal for measuring output power.
A typical RF output stage of the transmitter will have some filtering mecha- nism to suppress unwanted signals from being transmitted. These unwanted signals can be classified as either harmonics or spurious signals. Harmonics are integer multiples of the primary transmitter frequency and therefore the frequency at which they appear is very predictable. Spurious signals are typ- ically image frequencies caused by internal mixing of an oscillator or clock frequency with the primary transmitter output frequency. Spectrum analyzers are ideal instruments to be used for both harmonics and spurious measure- ments. Typically, harmonics are measured to at least the 5th harmonic [11].

6. 
   Receiver Tests
   

The WiMAX receiver requirements are defined in Section 8.3.11 of IEEE 802.16-2004. The receiver tests include receiver sensitivity, receiver adjacent and alternate channel rejection, receiver maximum input signal, receiver maximum tolerable signal, and receiver image rejection.
The test for receiver sensitivity measures the receiver’s performance using known signal conditions that include the modulation and coding rate, SNR, and input level. Using the specified conditions (given in IEEE 802.16-2004, Section 8.3.11), the receiver must be able to decode data bits with a bit error rate (BER) less than 10⁻⁶ after forward error correction (FEC). The standard specifies the test conditions for a variety of bandwidths and modulation types. To measure receiver sensitivity, the RF signal generator is set (using soft- ware methods) to generate the test conditions defined in the standards. Any connector and cable losses between the RF source output and the DUT input must be compensated by adjusting the RF output level at the generator. The DUT is set to receive and decode a continuous stream of packets that contain the special data patterns defined in the standards. The DUT must somehow calculate BER or provide the data bits externally to the BER test set that can calculate BER by comparing the received data bits with the expected values. The BER calculation is done on fully decoded payload data that does not contain FEC. The above procedure is repeated for all valid modulation and
coding types.
The other receiver tests can be performed as variations of the receiver sensitivity test described above.

3.