Optimizing and Testing WLANs phần 1 pot

[...]... dynamic standards body, the number of protocols grows by leaps and bounds every year IEEE 802 .11 subgroups are known as Task Groups (TGs), and are assigned letter suffixes to distinguish one from the other The standards documents that they create are also assigned 4 IEEE 802 .11 WLAN Systems IEEE 802 .11 802 .11 MAC 802 .11 PHY 802 .11 e 802 .11 i 802 .11 a 802 .11 b (QoS, 2005) (Security, 2004) (5 GHz OFDM, 19 99)... generation and distribution of encryption keys Similarly, the 802 .11 e standard added QoS functions to 802 .11 networks In addition to defining the EDCA and HCCA prioritized medium access methods, the 802 .11 e standard 10 IEEE 802 .11 WLAN Systems provided mechanisms to perform admission control (i.e., preventing the network from being overloaded) and traffic management Other 802 .11 letter suffixes (802 .11 k, 802 .11 r,... WG began work on extending these same data rates to the 2.4 GHz band shortly after 802 .11 a was published The result was the 802 .11 g standard, which incorporated all of 802 .11 b for backwards compatibility, and added the OFDM modulation types from 802 .11 a as well, producing a plethora of data rates: 1, 2, 5.5, 6, 9, 11 , 12 , 18 , 24, 36, 48, and 54 Mb/s (The specific data rate to be used is selected by the... standards documents that will eventually be folded into the main 802 .11 standard, while uppercase letters indicate that the document will remain permanently stand-alone Thus the output of the 802 .11 b group was folded into the main 802 .11 document in 2003 (forming Clause 18 ), but the 802 .11 T group is creating the 802 .11 .2 document, which will remain as a stand-alone performance test specification .1 1.2 .1. .. indicates the coding and length of the encapsulated MAC frame; the receiver then uses this to properly decode the frame The PLCP frame transmitted by an 802 .11 b radio is shown in the figure below The 802 .11 a standard was approved after the adoption of the 802 .11 b standard (Actually, work on the 802 .11 a standard was started prior to 802 .11 b, but as it used a much more 6 IEEE 802 .11 WLAN Systems Sync (Scrambled... technology As a result, in 19 90 the IEEE standards development organization set up a group, referred to as the IEEE 802 .11 committee, to standardize WLANs in the ISM bands However, it took 7 years (until 19 97) before the first 802 .11 standard was ratified and published That first standard defined a relatively low-speed digital WLAN technology, with data rate options of 1 and 2 Mb/s, and using a new Carrier... more efficient and flexible, and FHSS was gradually abandoned; no vendor sells 802 .11 FHSS radios today Subsequently, the 802 .11 b standard added Complementary Code Keying (CCK) at 5.5 and 11 Mb/s data rates to the mix, in addition to carrying forward the 1 and 2 Mb/s data rates of the original The following figure shows the general process used in CCK modulation See Clause 18 of IEEE 802 .11 for more information... Service Length CRC (12 8 bits) (16 bits) (8 bits) (8 bits) (16 bits) (16 bits) Long PLCP Preamble (14 4 bits at 1 Mb/s) Frame MAC Frame Long PLCP Header (48 bits at 1 Mb/s) Sync (Scrambled Zeros) SFD Signal Service Length CRC (12 8 bits) (16 bits) (8 bits) (8 bits) (16 bits) (16 bits) Short PLCP Preamble (72 bits at 1 Mb/s) MAC Short PLCP Header (48 bits at 2 Mb/s) Figure 1. 4: 802 .11 b PLCP Frame complex... Length Parity Tail (4 bits) (1 bit) (12 bits) (1 bit) (6 bits) Long Training Sequence PLCP Preamble (12 symbols) Signal Service (24 bits) (16 bits) MAC PLCP Header Frame Tail (6 bits) Pad Trailer Figure 1. 6: 802 .11 a PLCP Frame The 802 .11 a PHY operates in the 5 .15 –5.825 GHz band, which suffers from indoor propagation limitations Due to market demand, therefore, the 802 .11 WG began work on extending... govern how WLANs are developed and operated By necessity, only brief explanations can be provided here; the reader is encouraged to consult the actual standards documents and other references for more information 1. 1 IEEE 802 .11 Wireless Local Area Networks Contrary to popular misconception, 802 .11 is not merely “wireless Ethernet.” Instead, 802 .11 WLANs use an entirely different network protocol and are . AmendmentsMAC Amendments IEEE 802 .11 802 .11 MAC 802 .11 PHY 802 .11 b (2.4GHz CCK, 19 99) 802 .11 a (5GHz OFDM, 19 99) 802 .11 g (2.4GHz OFDM, 2003) 802 .11 h (Spectrum management) 802 .11 j (4.9GHz Japan, 2004) Task. 10 9 5 .1 An Introduction to Protocol Testing 10 9 5.2 Conformance and Functional Testing 11 1 5.3 Interoperability Testing 11 7 5.4 Performance Testing 12 1 5.5 Standardized Benchmark Testing 13 3 Chapter. Test 18 1 8 .1 Enterprise WLANs 18 1 8.2 Hot-spots 18 8 8.3 The Site Survey 19 0 8.4 Propagation Analysis and Prediction 19 6 8.5 Maintenance and Monitoring 202 Chapter 9: Testing MIMO Systems 207 9.1