1. CCRI J. Bernardini 1 IEEE 802.11g Characteristics Following is not in the Course textbook but is an important topic. The material is based upon several whitepapers Jerry Bernardini

2. 802.11 Summary Characteristics CCRI J. Bernardini 2 Protocol Release Date Op. Frequency Throughput (Typ) Data Rate (Max) Modulation Technique Range (Radius Indoor) Depends, # and type of walls Range (Radius Outdoor) Loss includes one wall 802.11a19995 GHz23 Mbps54 MbpsOFDM~35 Meters ~120 Meters 802.11b19992.4 GHz4.3 Mbps11 MbpsDSSS -CCK~38 Meters ~140 Meters 802.11g20032.4 GHz19 Mbps54 Mbps OFDM & DSSS ~38 Meters ~140 Meters 802.11n June 2009 (est.) 2.4 GHz 5 GHz 74 Mbps248 Mbps OFDM MIMO ~70 Meters ~250 Meters CCK-Complementary Code Keying OFDM-Orthogonal Frequency Division Multiplexing DSSS-Direct Sequence Spread Spectrum MIMO-Multi-Input Multi-Output

3. 802.11g Requirements Backward compatible with 802.11b Higher throughput than 802.11b Mixed mode operation CCRI J. Bernardini 3

4. 802.11g Protection Before an 802.11g client can transmit to an 802.11g AP it must reserve the medium. Must transmit so 802.11b will understand. Two Protection Methods –CTS-to self at 802.11b modulation (slow Clear to Send) –RTS-CTS at 802.11b modulation CTS-to-self is more efficient but may not be seen by hidden-node RTS-CTS is more reliable but has more overhead Both Methods dramatically reduce the 802.11g throughput CCRI J. Bernardini 4

5. 802.11b/g Mixed Mode Operation CCRI J. Bernardini 5 AP 802.11g Station 802.11g Station 802.11b 1-Slow CTS 2-Slow CTS 3-Fast Data 2-Slow CTS

6. Protection Throughput Effect Technology Transactions per second Mbps of TCP payload throughput Transactional speed relative to 802.11b 11b, 11 Mbps4795.61.0 11a, 54 Mbps2,33627.34.9 11g, 54 Mbps/no protection 2,33627.34.9 11g, 54 Mbps/CTS- to-self protection 1,11313.02.3 11g, 54 Mbps/RTS/CTS protection 7508.81.6 Based on Matthew Gast, 802.11 Wireless Networks: The Definitive Guide CCRI J. Bernardini 6

7. 802.11g Conclusions 802.11g is significantly faster then 802.11b for all conditions 802.11b station associating with a 802.11g network drops throughput due to protection 802.11b station does not have to be active to reduce throughput (just associated ) Mixed 802.11b/g deployments are likely to be common for the foreseeable future Mixed 802.11b/a deployments will have higher throughput 802.11b/g/n will also have to provide protection CCRI J. Bernardini 7

8. 802.11g References 1.When is 54 not equal to 54? A look at 802.11a, b, g Throughput, Matthew Gast, www.oreillynet.com/lpt/a/4085 www.oreillynet.com/lpt/a/4085 2.The New Mainstream Wireless LAN Standard, IEEE802.11g White Paper, Broadcom, www.54g.org/802.11g-WP104-Rwww.54g.org/802.11g-WP104-R 3.IEEE 802.11g New Draft Standard Clarifies Future of Wireless LAN, William Carney, Texas Instrument 4.The IEEE 802.11g Standard for High Data Rate WLANs, IEEE Network, May/June 2005 5.Intersel triples 802.11g date rates, Tony Smith, The Register, 16 April 2003 6.Maximizing Your 802.11G Investment, White Paper, Proxim Wireless Networks, 2003 7.Deploying High Capacity Wireless LANS, White Paper, Cisco Systems 8.Project: Wireless Throughput, Adrian Fisher, AVF0714@ecu.edu, April 12, 2007AVF0714@ecu.edu CCRI J. Bernardini 8