Crack WiMAX Physical Layer Test bottleneck

The development of WiMax technology also puts forward higher requirements for receiving and transmitting tests corresponding to WiMax physical layer tests. R & S provides targeted testing solutions.

WiMAX is called World Interoperability for Microwave Access. It is a wireless MAN technology ), A base station can provide a maximum downstream data transmission rate of Mbps for multiple fixed users within a 3-10 km radius, and provides a maximum downstream data transmission rate of 15 mbps for multiple mobile users within a 3 km radius. WiMAX currently has two major international standards: IEEE802.16-2004 and IEEE 802.16e-2005. IEEE802.16-2004 is a revision of 802.16a and 802.16d, which is mainly used for fixed broadband wireless access, including OFDM and OFDMA technology. IEEE 802.16e-2005 is an extension of IEEE802.16-2004 standard, it adds support for mobile broadband data access.

Physical Layer Test

In WiMAX technology, OFDM is used as the signal transmission mode for NLOS. As we all know, OFDM signals are composed of some orthogonal carriers, each of which is Digitally Modulated. Compared with single-carrier technology with the same data rate, OFDM signals have a longer symbol period, this technology has a strong performance against multi-path fading. In addition, the modulation methods used on the carrier are BPSK, PSK, 16QAM, and 64QAM. Various Modulation Algorithms are automatically switched according to the transmission rate requirements. Compared with WLan, WiMAX signal bandwidth is not fixed and can be changed from 1.25MHz to 28 MHz. In the IEEE802.16-2004, there are two modes: OFDM and OFDMA. In the OFDM mode, there are 200 sub-carriers and can work in TDD or FDD mode; In the OFDMA mode, the number of sub-carriers is variable, and each user is allocated a carrier group (sub-channel) to transmit the user data. The number of carriers is greatly increased. 802.16e-2005 supports mobile or roaming broadband data access. The Korean Standard WiBro is a special 802.16e technology.

For WiMAX devices, Physical Layer Testing (RF testing) is an essential means to ensure good quality and normal operation. Tests are divided into receiver and transmitter tests. In addition, amplifiers and other devices require similar testing processes. According to the requirements of WiMAX testing, R & S has released devices for generating and analyzing WiMAX signals, which can fully test the receiving and transmitting parts, to fully evaluate WiMAX devices.

Receiver Test

R & S Digital Signal Source SMU, SMJ, and SMATE with the corresponding WiMAX option SMx-K49 can support various types of WiMAX signal generation, including signal frame content configuration, channel coding and so on. Using this device, you can generate the desired WiMAX signal for receiver testing.

WiMAX signal generation

In SMU, IEEE802.16-2004, 802.16e-2005 and WiBro signal can be generated. During signal generation, important parameters of the signal are set according to the test requirements. Such as physical layer mode (OFDM/OFDMA), duplex mode (TDD/FDD), uplink and downlink, frame structure, Zone/Segment, signal bandwidth, modulation mode, burst type, Data Length, sub-channels.

WiMAX signal generation has the following features: in OFDMA mode, up to eight zones are supported, and each Zone can be configured separately, its type can be set to FUSC, PUSC, AMC2 × 3, or Sounding. In OFDMA mode, Burst Channel encoding supports CC and CTC.

Supports empty-time Encoding. MatrixA or MatrixB can be used together with the design concept of SMU dual-channel to easily generate two-channel signals with fading emission diversity.

Fading Simulation

To test the performance of WiMAX receivers, especially 802.16e, tests in fading environments are particularly important. SMU200A has a built-in Fading Simulator that can simulate a fading environment with a single channel of 40 or a double channel of 20 diameter. Each path can be set with corresponding parameters, such as loss, delay, moving speed, and Doppler frequency shift. Currently, the SUI (Stanford University Interim) model (SUI1-SUI6) can be used to test WiMAX fading. In the decline simulator of SMU200A, the SUI model is predefined and can be called directly by users.

MIMO

MIMO (Multiple Input Multiple Output) technology increases bandwidth utilization efficiency by implementing space multiplexing in antenna systems. It has been widely used in new high-speed data service systems, such as 802.11n, LTE, wiMAX. Therefore, MIMO is an essential part of WiMAX testing.

SMU200A has a dual-channel design concept. Each channel can independently generate the required WiMAX signal. In the specific WiMAX signal configuration, the corresponding empty-time encoding is supported to distinguish the signals of different antennas; in addition, the Fading Simulator of SMU200A can work in two channels, and the correlation between the two fading channels can be set. Therefore, SMU200A can fully support the test of Transmit Diversity (2 × 1) and receive diversity (1 × 2. For 2x2 MIMO or MIMO with more than 2x2 MIMO, such as beamforming, R & S will launch a Implementation Scheme Based on SMU200A in the near future. Therefore, SMU200A supports all MIMO tests in WiMAX.

Transmitter Test

The signal analyzer FSQ of R & S works with the corresponding WiMAX option FSQ-K93 to analyze various WiMAX signals, including the characteristics of the frequency domain, Time Domain Characteristics and modulation quality. Using this device, you can perform a complete WiMAX transmitter test. In FSQ, the analysis results of WiMAX signals are displayed in the numerical list.

In the Value List, the test results include EVM, IQ unideal, frequency domain and time domain power, symbol clock error, frequency error, CINR, RSSI, Crest Factor, and guide BER. In addition, FSQ provides graphic results of many analysis parameters, including: EVM corresponds to symbol and carrier variation, phase frequency error corresponds to Preamble variation, and spectrum flat, group latency, constellation chart, bit stream, Burst statistics, spectrum emission template (IEEE, ETSI), adjacent channel power, and CCDF.

In addition, FSQ also has the following features: For 802.16e-2005 OFDMA signals, FSQ supports automatic demodulation, that is, FSQ can automatically analyze the MapBurst information contained in the signals, the demodulated analysis results are automatically obtained without manually configuring the frame content of the analyzed signal. FSQ can automatically load the configuration file of WiMAX signal from the signal source (for example, SMU200A) through the LAN, making the analysis process easier, especially suitable for testing devices such as amplifiers. In addition, R & S will launch signal analysis solutions for MIMO testing in the near future, and even include multi-channel analysis functions of phase coherence. It can be seen that the FSQ of the signal analyzer can analyze various WiMAX signals to make a comprehensive assessment of the quality of WiMAX transmitters.

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