Hybrid wireless networks:
Hybrid wireless networks even though are very promising domain, in this area research is not now still intensively discovered. Main important research is presented; the aspects which are treated as major will consider routing, radio resources management, security and architectures. Afterwards existing type classifications are developed for the hybrid wireless networks.
In fact there are some contributions associated to the protection. The effort in Unified Cellular and Ad-hoc Network architecture (UCAN) offers security on attacks of selfish nodes. Avoiding the Individual hosts from eliminating legitimate hosts or making non-authorized hosts toward the relaying nodes set. But, this security has partial to the non colluding nodes. The Capkun et al. permits the anonymity and mobile hosts privacy sheltered with various access points in a hybrid wireless network .
Introduced the routing protocol based on secure tree, secure routes set up between the MNs and BS. An AAA (authentication, authorization and accounting) system is projected on public key cryptography by Zhang et al. used by the virtual notion operator, by this approach joins both the process of authentication, authorization and accounting and sending data to the IP layer, and permits ad hoc thus it mitigates attack of selfish nodes; though it will not combine layer 2 security devices which causes vulnerable to a large extent of layer 2 and attacks of DHCP.
Lastly, some work modified 802.11i protocol for hybrid ad hoc network, Shaer et al. suggest a secure handoff system combining the infrastructure mode and wireless networks ad hoc mode. An increased framework of 802.11i is executed increasing the APs functional range and approving the 802.11i security benefits. But, this type of scheme is not personalized to the common hybrid network situation as it may not manage in every mobile not less than two hops. 802.11i has adapted in vehicular contacts on highways. Other architecture is projected presenting contact between vehicles and also vehicular link to the Internet. Vehicles are the Ad hoc networking which is used to increase the Zone of 802.11 AP, with intermediate nodes. But this approach may not suggest a mobility management result.
Algorithms of Power control can abuse channel differences to increase the fairness and act. This can be obtained by opportunistically influencing the instant or past channel quality information achieved with dimensions and feedback. Effort on pioneer power control in downlink involves.
The main opportunistic power control idea is to use more power and enhance rate as improves the channel quality, and to prevent by the channel under an optimized stop. Example, in transmission of uplink in a fading channel of frequency-flat, to increase the overall throughput, just a sequence of user by achievement of the total best channel must be permitted to send its information at any period of time. Opportunistic power control may also carry advantages to a network when the users usually fit in to two precedence groups, example, transmission in cellular network which is higher priority for voice and lower priority for data.
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