Rough notes by Les Cottrell
Two flavors of spread spectrum both at 2.5GHz. Direct Spread Spectrum (DSSS), one piece PCMCIA radio product, 1, 2,5.5 & 11Mbps. Fully compliant 802.11 all speeds. 802.11b is DSSS.
Frequency Hopping Spread Spectrum (FHSS), one piece PCMCIA radio product, fully compliant 80211 only 1 and 2 Mbps. More for multipath topologies. It is lower coverage and lower thruput.
Cell phones are at 902-902.8 MHz, the Aironet is 2.4-2.4835GHz (IEEE 802.11). There is a new range 5GHz IEEE 802.11 for 54MHz 802.11a will ship next year. There may be a problem with the accelerator using a 2.4GHz 3rd harmonic. SLAC is using 2.4GHz phones which work so that could also cause problems.
Spread spectrum RF technology data is sent over airwaves, for 2-way radio communication, Cisco designs & manufactures its own radios, same radio frequency to send & receive. No licenscing required for Aironet Wireless products.
IEEE 802.11 standard in Jul 1997. 802.11b standard in September 1999, it is theonly RF tecnhnology defined DSSS @ 11Mbps. 802.11 offers true interoperability between vendors.
Will need a site survey from Cisco (required before sale) to find out which frequencies to use and coverage etc. 2Mbps is 350 ft radius, 5Mbps 175ft, 11Mbps is 125ft. Can go through 4-5 internal walls, or 1 brick wall. In Fall will ship 802.11b with 22Mbps, may be different distance limitations.
Scalability is the ability to locate more than one Acces Point (AP) in the same area increasing the bandwidth of that area for all users local to that AP. DS has a limit of 3 non-overlapping channels and therefore limits the total AP number to 3, so can support 33Mbps aggregate for all clients. FH can have as many as 15 AP colocated APs before collisions on hopping channels reduce effective data rate.
All Aironet wireless LANs deliver roaming. They claim more 802.11 options than any competitor. Client probes for APs. Evaluates AP beacon to determine best path (signal strength & noise). Can move from AP to AP and will automatically shift (but within subnet)
Security is based on data encryption (128bit - strong encryption & 48 bit) with Wired Equivalent Privacy (WEP). Inherent security of spread spectrum. Upcoming security enhancements: certificate server for authentication & centralized security management with multiple certificate server support and X.509 conformance. Question whether there is a key for each host or one shared key for all hosts. By default uses a single shared key. If want non-shared key then need PKI support.
Two products, one within building to support mobile users connectivity, the other to connect building with line of site. There is an ad-hoc mode where clients connect direct one to another, can be more than 2 clients in such a cell. There is no security.
The other mode uses APs. To prevent interference between cells the APs must not have 3 overlapping cells. Can have redundancy with > 1 AP on same channel.
Cisco 340 - 2.4GHz DS. APs have 10/100Mb Ethernet, there are PCMCIA & PCI cards & ISA. There can be 2048 clients on an AP. Configration is stored in NVRAM so can power off. AP341E2C dula integral antennas 2048 users, 128 WEP, AP341E2R slightly more powerful antenna. The PCMCIA cards are $199-399 (more expensive have more security, $240 is WEP 128bit price). PCI is $349, ISA is #349The AP is about $1099 - 1300 (upper end is 128 bit WEP).
APs have a menu driver configuration, minimum setup required for normal operation (plug & play for default operation), max flexibity with option menus, internal testing RF link. Configuration managememnt methods include: HTML web browser, BOOTP/DHCP, SNMP, telnet, FTP (all look like plain text with no security).
These are used to extend the LAN between buildings with line of site. Can get up to 25miles with 2Mbps, 11-12 miles for 11Mbps. Also support point to multipoint via an omni-directional antenna. Could use for distributing LANs in auditorium. The 802.11 spec limits distances to AP with directional antenna up to 1 miles @ any datarate. The bridge goes 25 miles at 2Mbps & 11miles at 11Mbps. The 340 bridge costs about $1889. Antennas are separate (e.g. $199 & lots of options).
Distance from antenna to bridge is 50feet.
Don't support Linux. Do support Windows 95, 98, NT & 2000.