Final Exam n Work 5 of 7 pages n 2-3 pages will be from the Fall ‘99 final n 85-90% Notes 10-15% Readings n Scheduled Date Wednesday, 3 May, Start Reviewing Now!

Homework n Readings: [19] “Speech Transmission Performance Planning in Hybrid IP/SCN Networks” [20] “Wireless Andrew: Bringing Mobile Computing to a University Community of ” [21] “MPEG-4: Multimedia for our time”

ISDN n n The all-digital phone network n n Covers OSI Layers 1-2, 3-7 n n Two types of access: 64Kbps B Channels (traffic) D Channels (signaling) n n Two standardized Interfaces BRI (2B + 16 Kbps D) - Home or Small Business PRI (23B + 64 Kbps D) - Larger Business

POTS Connectivity via BRI ISDN Phone CO Fiber Optic Trunk Copper Local Loop Copper Local Loop 4 Wire 2 Wire ‘4 Wire’ Digital 64 Kbps

Status of ISDN n n Too Little, Too Late for large businesses n n SOHO & home sales had been reviving, but trouble has arrived...   Cable Modems   Digital Subscriber Lines n n B-ISDN (> 1.5 Mbps speeds)   High Speed One-Stop Digital Network   Run over ATM n n Voice calls will eventually be all-digital, but maybe not as envisioned with ISDN

Cellular Telephony Advantages: n n Frequency Reuse n n Reduced Transmitter Power Out n n Reduced Multipath Problems n n Reduced brain damage? n n Subdividing Cells increases System Capacity n n More Reliable due to cell overlap

Cellular Telephony Disadvantages: n More complex n More installation hassles n BS to MTSO link & switching requirements can get out of hand

Cellular Telephony - Operation n Power Up & Intermittantly Thereafter Mobile communicates with BS/MTSO Local MTSO notes in database mobile is active If mobile is roaming, Home MTSO is notified via SS7

Cellular Telephony - Operation n Mobile to Wired call Mobile transmits # to BS/MTSO Unused voice RF channel (2 frequencies) is assigned Mobile tunes to assigned channels BS & MTSO coordinate TDM time slot MTSO places call via CO to wired unit

Cellular Telephony - Operation n Wired to Mobile call Call is placed to home MTSO Home MTSO pages mobile or forwards call to appropriate local MTSO, which pages mobile Unused voice RF channel (2 frequencies) is assigned BS & MTSO coordinate TDM time slot Mobile tunes to assigned channel, rings

Cellular Telephony - Operation n Handoff MTSO/BS/Mobile decides signal getting too weak Adjacent cells are polled Unused voice RF channel in the new cell is assigned Mobile tunes to assigned channel MTSO reroutes traffic: Old BS MTSO to New BS MTSO Takes about 100 msec with AMPS

Cellular Flavors n n AMPS (analog) u u uses FDMA and 30 KHz FM channels u u Can move data ( < 14.4 Kbps) n n IS-54/IS-136 TDMA (digital) u u 3x to 6x AMPS capacity using FDMA & TDMA u u Can move data ( < 14.4 Kbps) n n IS-95 CDMA (digital) u u a.k.a. Spread Spectrum u u probable 8-10x AMPS capacity u u Can move data ( < 14.4 Kbps )

FDM FDMA frequency time Different channels use some of the frequency all of the time. Example: AMPS Cell 1 Cell 1 Cell 2 Cell

TDMA/ FDMA frequency time Combo of TDM & FDM Example: IS-136, GSM etc Cell 1 Cell 1 Cell 2 Cell 2

+1 time Traffic (9 Kbps) Spreading Signal 27 Kbps Transmitted Signal 27 Kbps +1 DSSS - Transmit Side

time Despreading Signal 27 Kbps Received Signal 27 Kbps time Recovered Traffic 9 Kbps DSSS-Receiver

time Despreading Signal #2 27 Kbps Received Signal 27 Kbps +1 + time Recovered Garbage at 2nd receiver +1

CDMA frequency time Different channels use all of the bandwidth all of the time. Example: IS-95 Channels use different codes. Other channels cause noise-like interference.

Cellular Flavors n n Personal Communications Services (PCS) u u Bandwidth auctioned off by FCC in mid ’90’s u u Initial offerings similar to cellular, but on higher carrier frequencies (low GHz) u u Ultimate Goal: Unify wireless architectures (cell phone, pager, cordless phone, etc.) and provide anytime, anywhere digital services   Personal Communicators   Personal Phone Number u u Standards used: IS-136, IS-95, GSM