Guide to Wireless Communication - Chapter 9 Notes

Definition: A Wireless Metropolitan Area Network (WMAN) is a technology designed to cover larger geographical areas than Wireless Local Area Networks (WLANs).
Primary Goals:
- Extend wired networks beyond a single location without the costs of high-speed cable connections.
- Enable user mobility throughout a metropolitan area as a high-volume data traffic connection between access points or cellular towers.

Concept of Last Mile:
- The last mile connection refers to the final leg of the telecommunications networks that deliver internet services from a telecommunications provider to a customer.
- Typically uses copper cabling, but more recently fiber-optic cables are utilized.
Challenges:
- Traditional wired connections can be very expensive to lease, costing thousands per mile.
Copper vs. Fiber-Optic:
- Copper connections need signal regeneration every 6,000 feet, leading to high maintenance costs.
- Fiber-optic has largely replaced copper connections due to its higher capacity for data.

Technology: Most WMAN technologies are based on microwave signals in the 3- to 300-GHz frequency ranges.
- Microwave towers are spaced 35 to 50 miles apart.
Fixed Wireless: Using wireless technology for last mile connections or interbuilding connectivity.
- Backhaul Connection: Connects internal infrastructure; uses microwave links between cellular towers and high-speed lines.

Broadband: Sends multiple signals at different frequencies (e.g., traditional cable TV).
Baseband: Sends only one signal at a time over a single frequency (e.g., Ethernet).

Definition: Optical wireless communication that uses infrared lasers to transmit data.
Advantages:
- Cost-effective compared to fiber-optic installations.
- Fast installation (hours compared to months for fiber).
- Can transmit up to 1.25 Gbps over 4 miles in full-duplex.
- Higher security due to IR transmission.
Disadvantages:
- Performance can be affected by atmospheric conditions.
- Requires line-of-sight and can be hindered by obstacles like tall buildings and weather conditions (fog).

Definition: Used for interconnections between buildings and cellular towers.
Characteristics: Point-to-point, line-of-sight links operating typically in the 18 GHz licensed frequency range.
- Supports data rates up to 4 Gbps.
Security: Employs various security measures and protocols; uses AES encryption.

Overview: An open-standard broadband MAN technology for wireless communication.
- Supports both line-of-sight and non-line-of-sight applications.
Components:
- Base Stations (BS), Subscriber Stations (SS), and uses protocols for interoperability.
Applications:
- Backhaul business applications, last mile delivery as an alternative to DSL and cable.
- Supports simultaneous transmission of voice, video, and data, which is referred to as "triple play".
Range and Throughput:
- Achievable distances vary with frequency; lower frequencies used for longer distances.

FSO Security: FSO systems are secure due to their line-of-sight nature, making it difficult to intercept signals.
Microwave Security: Implements its own security protocols with encryption standards (128/256-bit AES).
WiMAX Security: Features a privacy sublayer with key management protocols, encryption (3-DES, RSA, AES) to secure communications.

WMANs leverage advanced wireless technologies like FSO and microwave communication to provide high-speed internet access over metropolitan areas, offering flexibility and cost efficiency compared to traditional wired solutions. Understanding the advantages, challenges, and technologies involved is crucial for optimizing network deployment and performance.