Unit 4
Page 1: Introduction
Title: Wireless Operations Unit no:-4 and its Standards Mobile Computing
Course Code: 09CE1501
Instructor: Prof. Rushi Raval
Page 2: IEEE 802 Overview
Definition: IEEE 802 is a family of standards that govern local area networks (LANs) and metropolitan area networks (MANs).
Functionality: It deals only with variable-size packets and pertains to the lower two layers of the OSI model - Data Link and Physical.
Layer Segmentation:
Logical Link Control (LLC): Manages protocols for the higher layer.
Media Access Control (MAC): Controls how devices on a network uniquely identify themselves and access the network.
Page 3: Standard Scope
IEEE 802.11 Standards: Various specifications of IEEE 802.11 standards focus on physical layers and provide enhancements for wireless performance.
802.11a: 5-GHz OFDM with a data rate range of 6 to 54 Mbps.
802.11b: 2.4-GHz DSSS with rates of 5.5 Mbps and 11 Mbps.
802.11g: Extension of 802.11b with higher data rates (>20 Mbps).
802.11n: Enhancements for higher throughput.
802.11ac: Focus on delivering 1 Gbps in the 5-GHz band.
802.11ad: Enhancements to support high-speed data rates in the 60-GHz band.
Page 4: Detailed Comparison of IEEE 802.11 Standards
Standard Years Introduced:
802.11a, b (1999), 802.11g (2003), 802.11n (2009), 802.11ac (2012), 802.11ad (2014).
Maximum Data Transfer Speeds:
802.11a: 54 Mbps
802.11b: 11 Mbps
802.11g: 54 Mbps
802.11n: Up to 600 Mbps
802.11ac: Up to 3.2 Gbps
802.11ad: Up to 7 Gbps
Frequency Bands: Ranges from 2.4 GHz to 60 GHz.
Page 5: Wireless LAN Structure
Extended Service Set (ESS): A configuration where Basic Service Sets (BSS) communicate through a distribution system.
Access Point (AP): Core element that connects the BSS to the overall network.
Page 6: Stations in WLANs
Stations (STA): Includes all devices connected to the wireless LAN: laptops, printers, smartphones, etc.
Types of Stations:
Wireless Access Points (WAP): Base stations in the network.
Clients: End-user devices requiring access to the network.
Page 7: Basic Service Set (BSS)
Definition: A BSS is a group of stations communicating at the physical layer.
Categories:
Infrastructure BSS: Communicates through access points.
Independent BSS: Peer-to-peer communication without AP.
Page 8: Extended Service Set (ESS)
Description: A network of interconnected BSS, providing broad coverage.
Distribution System (DS): Connects multiple access points and enhances communication.
Page 9: Advantages of WLANs
Clutter-Free Environment: WLANs eliminate the clutter caused by cables.
Scalability: Easy to add or remove devices from the network.
Portability: Users can access the network from various locations without wire constraints.
Easier Setup: Installation costs and time are significantly lowered compared to wired LANs.
Page 10: Disadvantages of WLANs
Signal Interference: More noise in communication due to radio signals, risking data integrity.
Higher Bandwidth Demands: WLANs require greater bandwidth and are slower than wired networks.
Page 11: Services Provided by 802.11
Station Services: Include essential functions like authentication and data transfer.
Distribution System Services: Facilitate the movement and organization of data within the network.
Page 12: Station Services Overview
Key Services: Authentication, de-authentication, privacy, and association with access points.
Page 13: Authentication Methods
Open System Authentication: Basic method where devices identify each other.
Shared Key Authentication: Uses a secret key for authenticating stations, enhancing security.
Page 14: De-authentication and Privacy Services
De-authentication: Notifies a station of disassociation; cannot be refused.
Privacy Measures: WEP algorithm encrypts messages to protect against eavesdropping, with initial unencrypted status.
Page 15: Association and Disassociation Services
Association: Initial connection to an AP for network access; vital for communication within the WLAN.
Disassociation: Formal termination of a connection, which cannot be refused by either party.
Page 16: Distribution and Integration Services
Distribution Service: Sends MAC frames across the distribution system.
Integration Service: Ensures smooth delivery of frames across access points.
Page 17: Reassociation Service
Purpose: Facilitates seamless transitions between access points as a user moves within the network, maintaining connectivity.
Page 18: Channel Allocation Overview
Channel Allocation Importance: Determines how communication channels are distributed and used within cellular networks.
Page 19: Categories of Channel Allocation
Types:
Fixed Channel Allocation
Dynamic Channel Allocation
Hybrid Channel Allocation
Page 20: Fixed Channel Allocation (FCA)
Operation: Static allocation of channels to specific cells; efficiency relies on frequency reuse.
Challenges: Calls can get blocked if all channels in a cell are occupied, impacting user access.
Page 21: Dynamic Channel Allocation (DCA)
Functionality: Allocates channels from a pool to cells as needed to handle non-uniform traffic.
Issues: Randomness and complexity in channel assignment can lower efficiency compared to FCA.
Page 22: DCA Problems
Limitations: Random methods may underutilize available resources and involve complex algorithms requiring heavy computation.
Page 23: Hybrid Channel Allocation (HCA)
Description: Combines FCA and DCA; utilizes fixed channels first, then draws from a dynamic pool as needed.
Goal: Maintain efficiency under varying traffic demands.
Page 24: Location Management Basics
Location Areas (LA): Groupings of network cells that allow mobile users seamless movement and communication.
Importance: Efficient location management quickens user paging and reduces operational costs.
Page 25: Location Management Strategies
Types: Static and dynamic management methods tailored for user movement and network efficiency.
Page 26: Static Location Management
Function: Updates based on user location changes or periodic checks.
Drawbacks: Can lead to unnecessary updates and costs due to overly frequent location changes.
Page 27: Visual Representation of Static Management
Illustrations: Show differences in user movement versus LA updates and potential pitfalls.
Page 28: HLR and VLR Architecture
Components: HLR (Home Location Register) and VLR (Visitor Location Register) form critical parts of location management within mobile networks.
Page 29: Dynamic Location Management
Advancements: Tailors location management strategies based on real-time user behavior and conditions.
Page 30: Parameters Affecting Location Management
Paging: Effective but may lead to excessive operations if not managed properly.
User Mobility: Determines how services are configured based on user movement patterns.
Page 31: Handoff Concept
Definition: The transition of an active call between cells or channels to ensure continuous service.
Also Known As: Handover; critical for maintaining connectivity.
Page 32: Handoff Scenarios
Trigger Factors: Moves between coverage areas, or exceeding cell capacity can initiate handoff.
Page 33: Handoff Types
Hard Handoff: Connection breaks during the transition.
Soft Handoff: Maintains at least one established connection, avoiding service interruption.