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It really can be a nightmare. All that gobbledegook terminology. We define a number of terms to help ease the wireless pain threshold:
Enlightenment: The 802.11 standards are now freely available in PDF format once they are over 6 months old.
| 16QAM | Modulation scheme. 16 - Quadrature amplitude modulation uses QAM with 4 amplitudes and 4 phases to allow 16 values to be transmitted. |
| 64QAM | Modulation scheme. 64 - Quadrature amplitude modulation uses QAM with 8 amplitudes and 8 phases to allow 64 values to be transmitted. |
| 802.11 | IEEE standard that is the base for wireless Lans. Defined the protocol that is used throughout the 11x group of standards. Supported a number of different PHYs (Phyical Layers) including FHSS (Frequency Hopping Spread Spectrum) and DSSS (Direct Sequence Spread Spectrum). Supported both wireless and Infrared (IR) media. Data rates up to 2Mb. ISM band 2.400-2.483.5 GHz. Modulation techniques - BPSK, QPSK. |
| 802.11a | IEEE standard. Uses the protocol defined in 802.11. DSSS (Direct Sequence Spread Spectrum) at data rates up to 54Mb. UNII band 5.15-5.25 GHz, 5.25-5.35 GHz, 5.725-5.825 GHz. Modulation techniques - 16QAM, 64QAM, QPSK, BPSK. |
| 802.11b | IEEE standard. Uses the protocol defined in 802.11. DSSS (Direct Sequence Spread Spectrum) at data rates up to 11Mb. ISM band 2.400-2.483.5 GHz. Modulation techniques - CCK, DBPSK, DQPSK. |
| 802.11g | IEEE standard. Uses the protocol defined in 802.11. DSSS (Direct Sequence Spread Spectrum) at data rates up to 54Mb. ISM band 2.400-2.483.5 GHz. Modulation techniques - OFDM with 16QAM, 64QAM, QPSK, BPSK and falls back 11b's CCK, DBPSK, DQPSK. |
| 802.11n | IEEE standard in progress. Proposes speeds up to 74 Mb with data throughput of u 270Mb. Not (as of 5/2007) ratified, target completion is March 2009. |
| 802.16 | IEEE wireless MAN standard (a.k.a. WiMAX). Operates in the licensed 10-66 GHz frequency range and provides speeds up 70 Mbps over distances to 31 miles. |
| BER | Bit Error Rate or Ratio (BER) defines the number of error bits received over time and is expressed as a negative power - thus a BER of 10-5 is one error per 100,000 bits of transmission. Wireline serial transmission typically has a BER in the 10-10 to 10-12 range whereas most radio systems are in the 10-3 to 10-6 range. |
| BPSK | Modulation scheme. Binary Phase Skift Keying uses PSK with two phases of 180o. |
| CCK | Modulation scheme. Complimentary Code Keying uses a systems of symbols encoded using DQPSK. Used in 802.11b to achieve the 5.5 and 11 Mb rates. |
| DPSK | Modulation scheme. Generic term. Differential Phase Skift Keying compares the value received in each phase to previous values. Implementations use DBPSK or DQPSK. |
| DBPSK | Modulation scheme. Differential Binary Phase Skift Keying uses DPSK with two phases of 180o. |
| DQPSK | Modulation scheme. Differential Quaternary or Quadriphase Phase Skift Keying uses DPSK with four phase shifts of 90o. |
| MIMO | Generic term. Multiple-input multiple-output refers to the use of multiple antennas at the transmitter and receiver and makes it paticularly useful for OFDM. Each sub-channel may be sent on an optimally designed antenna thus increasing the reliability of the complete transmission. |
| OFDM | Multiplexing scheme. Generic term. Orthogonal Frequency Division Multiplexing divides a single frequency into multiple sub-frequencies each of which is independent (orthogonal) and may use different modulation techniques (such as BPSK or 16-QAM). Since the characteristics of each sub-channel are different, and hence subject to varying interference patterns, this allows more reliability in reception of the complete transmission. |
| PSK | Modulation scheme. Generic term. Phase Skift Keying in which the absolute value received in each phase is used. Implementations use BPSK or QPSK. |
| QAM | Modulation scheme. Generic term. Quadrature amplitude modulation uses values from two carriers which are out of phase by 90o modulated to create a single output. By using different phases and varying the amplitude combinations are created such as 4 phases (90o) x 4 amplitudes = 16 (16-QAM). Implementations typically use 16-QAM, 64-QAM, 128-QAM and 256-QAM. |
| QPSK | Modulation scheme. Quaternary or Quadriphase Phase Skift Keying uses PSK with four phase shifts of 90o. | Wi-Fi | Term used to define wireless devices that are certifie by the Wi-Fi Alliance and hence will inter-operate with other such devices. Standards used are based on the IEEE 802.11 series. | WiMAX | WiMAX (Worldwide Interoperability for Microwave Access) is an industry coalition formed to advance the 802.16 standards by certifying inter-operability between products. Similar objective to Wi-Fi. |
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