On 16/11/2010 21:37, Charles Craft wrote: > On 11/16/2010 2:59 PM, Michael Watterson wrote: >> On 16/11/2010 18:35, Charles Craft wrote: >> >>> Do you have a link to your wireless ISP? >>> What's the distance between your antenna and their end? >>> >> 12.5km >> >> www.digiweb.ie >> > That's pretty sweet - "The antenna is small and unobtrusive, effectively > a 12cm square plastic box." My latency is about 20ms to 30ms, typically 22 to Irish sites. It saves the usual cost of oven reference for the 20MHz DOCSIS upstream=20 to 10.6GHz conversion by using a single 9.7GHz approx L.O. in an PLL, The Base station has a pilot at 10.252GHz. A 495MHz approx pilot=20 receiver locks the Microwave L.O. used for downconversion. The indoor Cable modem is thus about 485MHz (there are 4 x 8MHz=20 channels) Downstream and about 20MHz upstream. This is mixed to about=20 820MHz and filtered in 2 x SAW filters and mixed the the single 9.7GHz=20 approx L.O. The LO. is spilt with wilkinson stripline to TX mixer and=20 then the other 1/2 split for PLL prescaler and RX down mixer. It uses a=20 PIC to control the two LMX series synth / PLL (the 800MHz 1st IF for TX=20 and the 9.7GHz syncronised to the off air 10.252GHz beacon). Obviously the Basestation uses Oven reference and up converts the CMTS=20 cable downstream to feed a 30W rated 10.25GHz approx PA at about 3W. And=20 Downconverts the 10.6GHz from domestic units to the CMTS IF in frequency.. So Cable Broadband, with only about 3m to 20m coax at each house and=20 full duplex X band microwave to headend. Some sites they have 3 x 28MHz=20 FDD allocations. In theory if you have LOS and put a dish instead of the=20 pair of PCB aerials (H &V for TX and RX, or vice versa), the system=20 could work to 180km (160km is the DOCSIS max plant length, but that is=20 coax, Radio goes further in same time). So newer VSAT is changing from Mix of DVB-S + DVB-RCS and proprietary=20 systems to a satellite version of DOCSIS. Wildblue in USA and Tooway in=20 Europe. More to Come http://www.techtir.ie/blog/watty/ka-sat-countdown DOCSIS over wireless is more efficient than Wimax and lower latency. But=20 no good for Mobility. Though oddly it can support Nomadic, (1min to 3min=20 sector re-connect) DOCSIS is also used at 700MHz and 800MHz. (Caribbean)? and can use ANY=20 bandwidth from about 2MHz to 10MHz per channel downstream by changing IF=20 filters and and Symbol Rate. 6MHz & 8MHz are of course standard US and=20 Euro channels used on all the Microwave DOCSIS, but Arriss does 2MHz=20 filtered Modems (you can use adjoining channels!) for the UHF DOCSIS=20 they sell branded WiDox :) Many Microwave bands available. DOCSIS=20 standard implementations use TDMA assigned slots by base CMTS for=20 upstream in 0.8, 1.6, 3.2 or 6.4MHz channels. QPSK to 32QAM possible. Since you simply need a full duplex transverter for HF & UHF to an FDD=20 band, it's easy to put DOCSIS on a new band. Digiweb has about 60K=20 subscribers on 5Mbps to 12Mbps (64QAM downlink) packages. There is also=20 an Irish ISP with 3.6GHz FDD DOCSIS (16QAM for longer range) DOCSIS 3.0 isn't so interesting for Wireless as it's bonding entire=20 channels. More Hybrid Fibre Cable operators. The Average DSL speed in Ireland is < 3Mbps The Average Cable speed is over 10Mbps (set to rise to over 30MBps) The Average Wireless DOCSIS is over 6Mbps My speed test just now on 8Mbps down, 1Mbps up package http://www.speedtest.net/result/1033367017.png Cable Modem Stats (12.5km microwave) *RX Power* 0 dBmV Frequency 485MHz *Signal to Noise Ratio* 29 dB *Modulation* QAM64 *Shared Upstream Data Rate* 5120 Ksym/sec *Modulation* QPSK *Power *44 dBmV Logical Channel 1 (I think about 20MHz) Real Downstream is about 10.248GHz, Upstream about 10.590GHz The PA transistor is regular MAR6 size package. mWs of power... Aerial=20 panel gain is about 17dBi I think.... N.F. of RX is about 2.5dB! Ordinary RG6 with 12V 600mA DC inserted connects cable modem to "Radio".=20 The Radio is under 200 Euro I think. Cable Modem with two phone jacks (2=20 x ATA) is under 50 Euro. Irish Line rental for copper is 26 euro a line. Before you add calls or=20 DSL. My package is about 40 Euro including two "lines" with real=20 numbers. I have DECT phones and fax. QOS, almost zero packet loss and low jitter and ISP has own SIP servers=20 and PSTN gateway means even Fax works. Or indeed the dialup modem built=20 into my laptop :-) --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .