The present chapter contains a thorough investigation of Quality of Service, Energy Conservation and mobility in 802.11 and 802.16 standards. Interest on these two technologies arises from the fact that they are designed to cooperate offering wireless access capabilities in Next Generation Networks (NGNs). Under NGN Wireless architectures, key challenges must be taken into account: (a) Broadband technologies are based on QoS Enabled Telecommunication Services; (b) Mobile devices are battery limited. In fact, how to prolong the life time of a mobile device and minimize power usage is a very important design issue; (c) Wireless operation means that the user is expected to roam freely, which must also be taken into account. The dependability of NGN operation is obviously depended on these three features.
Two very important features of the Wireless Next Generation Networks (Wireless NGNs) are the energy consumption and the mobility of terminals. Energy consumption constrains the infinite bandwidth-roaming space of a wireless terminal and therefore it requires a careful power saving strategy every time that a communication endpoint needs to reside to battery life. On the other hand, the term mobility has been used to describe many different aspects of a wireless network like the movement of the wireless nodes (cellular networks mostly), the ability to transfer network layer settings (like mobile IP) and the handover theory. This chapter is dedicated to study of power saving mechanisms, Quality of Service (QoS) and handover mechanisms in modern wireless networks in view of the forthcoming Wireless NGNs. These mechanisms are necessary to combat the problems that arise from mobile wireless communication and make this capability efficient, transparent and above all possible.
Key Terms in this Chapter
FBSS: Fast BS switching.
TIM: Traffic Indication Map.
VOIP: Voice over IP.
TC: Traffic Classes.
MAC: Medium Access Control.
TxOP: Transmission Opportunity.
BS: Base Station.
EOSP: End of Service Period.
QAP: Quality Enhanced AP.
MSISDN: Mobile Subscriber ISDN.
ISDN: Integrated Services Digital Network.
CAHN: Cellular Assisted Heterogeneous Networking.
TS: Traffic Streams.
ATIM: Announcement (or Adhoc) Traffic Indication Message.
BSS: Basic Service Set.
HTTP: Hypertext Transfer Protocol (World Wide Web protocol).
DIFS: Distributed Interframe Space.
U-APSD: Unscheduled APSD.
S-APSD: Scheduled APSD.
DSL: Digital Subscriber Line.
HCF: Hydrid Coordination Function.
WEP: Wire Equivalent Protocol.
SIFS: Short Interframe Space.
CFP: Collision Free Period.
SS: Service Station.
MS: Mobile Station.
VoWLAN: Voice over WLAN.
IBSS: Independent Basic Service Set.
BE: Best Effort.
AP: Access Point.
CW: Contention Window.
EDCA: Enhanced Distributed Coordination Access.
PCF: Point Coordination Function.
PS-Poll: Power Save Poll.
IP: Internet Protocol.
HCCA: Hydrid Coordination Access Method.
APSD: Automatic Power Save Delivery.
PSM: Power Save Mechanism.
MDHO: Macro Diversity Handover.
CP: Collision Period.
CSMA/CA: Carrier Sense Multiple Access/Collision Avoidance.
DCF: Distributed Coordination Function.
MSDU: MAC Service Data Unit.
CWmin: Contention Window Minimum.
AIFS: Arbitrary Interframe Space.
DTIM: Distributed Traffic Indication Message.
PIFS: Priority Interframe Space.
Wi-Fi: Wireless Fidelity.
ADDTS: Add Traffic Stream.
CAP: Controlled Access Phase.
QoS: Quality of Service.
RADIUS: Remote Access Dial-In User Service.
WLAN: Wireless Local Area Network.
QSTA: Quality Enhanced STA.
MDL: More Data.
CWmax: Contention Window Maximum.
LI: Listening Interval.