1. EE360 – Lecture 1 Outline Course Overview Potential Course Topics Broadcast Channels MAC Channels Duplexing FD, TD, and CD

2. Potential Course Topics Broadcast and MAC Channels –Capacity regions (fading and ISI) –Resource allocation/adaptive modulation –Multiple antennas –CDMA and multiuser detection –Multirate/multimedia –Random access Cellular Systems –Capacity and area spectral efficiency –Resource allocation/adaptive modulation –Multirate/multimedia –Multiple/smart antennas Ad Hoc Networks –Capacity –Multihop routing –Throughput and Delay –Energy constraints HW0: Pick two topics related to these broad areas and find one paper on each for possible class presentation (due 3/11)

3. Broadcast Channels Synchronization easy. Interference signals follow same path as desired signal (no near-far problem) Complexity/power at transmitter less restricted than at receiver.

4. Multiple Access Channels Synchronization overhead required. Interference signals follow different paths than desired signal (near-far problem) Complexity/power at receiver less restricted than at transmitter. MAC channel is limiting factor in cellular systems with symmetric traffic.

5. Duplexing Separation of uplink and downlink traffic Frequency Division Duplexing-FDD: uplink and downlink traffic sent in different frequency bands. –No synchronization issues. –Uplink and downlink channels may fade indepently. –Duplexor required to separate signals Time Division Duplexity- TDD: uplink and downlink traffic sent on different timeslots. –Simple duplex equipment –requires synchronization –need guard bands to prevent overlap –transmission in one direction can be used to measure channel in other direction. –Flexible bandwidth allocation between uplink and downlink.

6. Code Division Duplexing Separate uplink and downlink using orthogonal or semiorthogonal codes Semi-orthogonal codes have insurmountable near-far problems. Orthogonal codes destroyed by multipath channel Not used in any existing systems.

7. Frequency Division Advantages –Narrowband channels (no ISI) –Low complexity –Allows cts. time transmission and channel estimation. Disadvantages –Multiple radios at base station –Handoff complicated by cts. transmission –Dedicated channels (idle ones wasted) –Difficult to allocated multiple channels per user Total system bandwidth divided into orthogonal channels assigned to different users. FD alone not used in current digital systems

8. Time Division Advantages –Common radio eqmt. for all users at the base station. –Noncontinuous transmission facilitates handoff and reduces power consumption. –Easy to allocated multiple channels/user –No duplexor required Disadvantages –Synchronization required –Multipath destroys slot orthogonality –Typically require ISI mitigation –Idle channels may be wasted –Short transmissions make equalization and dynamic resource allocation hard. Time divided into orthogonal slots, with different timeslots assigned to different users.

9. Code Division Advantages –No hard limit to # of users in system (soft capacity - system is interference-limited) –Interference reduction techniques increase capacity –Synchronization not required –Can allocated multiple “channels”/user using multicode or multirate techniques. Disadvantages –Complexity –Near-far problem Orthogonal or semi-orthogonal codes used to modulate each users signal. Code properties used to separate users at the receiver.

10. Examples AMPS FDMA/FDD GSM (EDGE)TDMA/FDD IS-54 and IS-136TDMA/FDD JDCTDMA/FDD IS-95CDMA/FDD IMT-2000CDMA/FDD