Unit 2: Wireless Standards

Introduction to Wireless Standards

In today's highly connected world, wireless standards are crucial to enable seamless communication across various devices and networks. Wireless standards define protocols and specifications for communication without physical connections, allowing devices to communicate over the air. These standards provide interoperability, efficiency, and security for wireless communication. Popular wireless standards include WLAN (Wireless Local Area Network), Bluetooth, and WiMAX, each catering to different use cases and providing specific features to optimize communication.

Definition and Purpose of Wireless Standards

Wireless standards, or wireless communication standards, are protocols that define the methods for data transfer over wireless networks. Each wireless standard specifies the frequency range, bandwidth, modulation techniques, and other technical parameters, enabling efficient communication among devices. By adhering to these standards, devices from different manufacturers can operate on the same network without compatibility issues. Wireless standards facilitate various applications, from local area networks to personal area networks and wide-area networks, each addressing specific performance, range, and data requirements.

The purpose of wireless standards includes:

1. Interoperability: Ensure devices from different manufacturers can communicate seamlessly.
2. Efficiency: Define techniques to optimize bandwidth, reduce interference, and manage network resources.
3. Security: Implement protocols that protect data from unauthorized access.
4. Reliability: Minimize data loss and maintain consistent communication.

Wireless Local Area Networks (WLANs)

Wireless Local Area Networks, commonly known as WLANs, enable devices to communicate wirelessly within a localized area, such as a home, office, or campus. WLANs operate on short-range radio frequencies to connect devices like laptops, smartphones, and tablets to the internet or other network resources. WLAN technology offers mobility, scalability, and flexibility without the need for extensive cabling, making it a preferred choice for most modern networking environments.

Fundamentals of WLAN

A WLAN uses radio waves to transmit data, eliminating the need for physical connections. WLANs typically operate within the 2.4 GHz and 5 GHz frequency bands, utilizing various protocols within the IEEE 802.11 family to manage communication.

Key Design Goals of WLAN:

1. Mobility: Support for seamless roaming without losing connectivity.
2. Scalability: Enable adding more devices without significantly affecting network performance.
3. Cost-effectiveness: Reduce infrastructure costs by eliminating cables and minimizing maintenance.
4. Reliability: Ensure consistent performance even in environments with multiple users.

Characteristics of WLAN

• Range: WLANs have a range of approximately 30 to 100 meters indoors and 100 to 300 meters outdoors.
• Bandwidth: Speeds range from 1 Mbps in early implementations to 10 Gbps with advanced standards like IEEE 802.11ax.
• Frequency Bands: Operate primarily in the 2.4 GHz and 5 GHz bands, with newer standards utilizing 6 GHz.

WLAN Network Architecture

A typical WLAN architecture consists of an Access Point (AP) and client devices. The AP acts as a bridge between the wired network and wireless devices, managing the data flow and ensuring communication security. WLANs can use either Infrastructure Mode (where all devices communicate via an AP) or Ad Hoc Mode (where devices communicate directly without an AP).

IEEE 802.11 WLAN Standard

The IEEE 802.11 standard defines the protocols for implementing WLANs. This standard includes various amendments, with each focusing on improvements in data rate, range, and network efficiency.

Components in an IEEE 802.11 Network

• Station (STA): A device equipped with a wireless network interface card.
• Access Point (AP): The network’s central hub, which broadcasts signals and manages data transmission.
• Basic Service Set (BSS): The foundational building block of an IEEE 802.11 network; includes an AP and connected STAs.
• Extended Service Set (ESS): A network of multiple BSSs connected by a distribution system.

IEEE 802.11 Physical Layer

The Physical Layer of IEEE 802.11 defines the modulation and coding schemes, transmission power, and frequency bands for data transmission. It includes techniques such as Direct Sequence Spread Spectrum (DSSS) and Orthogonal Frequency Division Multiplexing (OFDM) to optimize data rates and reliability.

IEEE 802.11 MAC Sublayers

The MAC layer in IEEE 802.11 manages channel access, addressing, and error checking. It has two sublayers:

1. Distributed Coordination Function (DCF): The primary mechanism for channel access, DCF uses Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) to prevent packet collisions.
2. Point Coordination Function (PCF): An optional mechanism that provides centralized control by allowing the AP to schedule communication.

Hidden and Exposed Station Problems

• Hidden Station Problem: Occurs when two devices are out of each other's range, resulting in potential collision since neither device is aware of the other’s transmission.
• Exposed Station Problem: Arises when a device incorrectly senses that the channel is occupied by a nearby transmission, preventing it from transmitting even though it would not cause interference.

IEEE 802.11 Frame Format

The frame format defines how data is structured for transmission. Each frame includes fields for the destination address, source address, payload, and error checking, allowing accurate data transfer between devices.

Addressing Mechanism in IEEE 802.11

IEEE 802.11 utilizes a unique addressing mechanism, with MAC addresses assigned to each device for identifying the source and destination of data packets within the network.

IEEE 802.15.1 Bluetooth

Bluetooth (IEEE 802.15.1) is a short-range wireless technology designed for personal area networks (PANs). Bluetooth enables communication between devices within a 10-meter range, typically used for connecting peripherals like headphones, keyboards, and printers.

Bluetooth Architecture and Layers

Bluetooth operates in the 2.4 GHz ISM band and employs frequency-hopping spread spectrum to minimize interference. Its architecture is structured into several layers:

1. Radio Layer: Defines physical characteristics like frequency and modulation.
2. Baseband Layer: Manages connection establishment, data transfer, and error checking.
3. Link Manager Layer: Handles connection management, device pairing, and security features.
4. Logical Link Control and Adaptation Protocol (L2CAP): Supports multiplexing, segmentation, and reassembly of data packets.

Bluetooth Operational States

Bluetooth devices operate in different states:

• Standby: The device is inactive and waiting for connection requests.
• Inquiry: The device searches for other Bluetooth devices.
• Page: Initiates a connection with another device.
• Connected: The device is actively communicating with another device.

IEEE 802.16 WiMAX

WiMAX (Worldwide Interoperability for Microwave Access) is a broadband wireless access standard designed for wide-area networks, often spanning several kilometers. IEEE 802.16 provides high-speed internet access in rural and urban areas where traditional wired infrastructure may be lacking.

WiMAX Services

WiMAX offers two main types of services:

1. Fixed WiMAX: Provides broadband access to stationary devices in locations such as homes and offices.
2. Mobile WiMAX: Offers internet access to mobile devices, enabling connectivity on the go.

WiMAX Architecture and Layers

WiMAX architecture consists of three main components:

1. Base Station (BS): The primary point of connectivity, managing network access and data flow.
2. Subscriber Station (SS): The device that connects to the base station, such as a WiMAX modem or mobile device.
3. Network Access Point: Connects the WiMAX network to external networks, such as the internet.

WiMAX layers include:

• Physical Layer: Defines the frequency, modulation, and error correction techniques for reliable data transmission.
• MAC Layer: Manages bandwidth allocation, error checking, and network access control.

Comparison of Bluetooth, IEEE 802.11, and IEEE 802.16