In this paper we derive performance metrics closed-form expressions of retransmission schemes such as Automatic Repeat reQuest (ARQ) and Hybrid ARQ (HARQ) in the case of memoryless block fading channels. As performance metrics, we consider the Packet Error Rate (PER), the efficiency, and the packet delay. The novelty of the paper is twofold: i) the metrics are considered at the Network level; ii) we introduce a new general framework which enables us to derive analytically the considered performance metrics for most retransmission schemes, including recent cross-layer strategies with the Network layer. The metrics at the Medium Access Control (MAC) level are obtained as a byproduct. Among the considered retransmission schemes, we especially consider the Incremental Redundancy HARQ scheme with different lengths redundancy packets.

In order to improve the reliability of any HARQ technique at the IP level, a cross-layer strategy between the MAC and the IP levels has been recently developed in. This strategy consists in replacing a retransmisssion credit per MAC packet with a retransmission credit per IP packet. In other words, the transmission credit is shared by the MAC packets belonging to the same IP packet. Packet Error Rate, throughput, delay and jitter for this new approach have been extensively analyzed in. In this paper, we remark and theoretically prove that the first MAC packets are better protected than the last ones. This leads to a natural "unequal packet loss protection" that can be useful in many applications, such as video streaming, compressed image transmission, audio and protocols (TCP/IP). Exploiting this novel manner of protecting packets unequally may not exclude the use of the standard manners, such as different feedforward error correcting codes (FEC), modulation size, or hybrid ARQ scheme per required quality of protection. Finally, our claims are supported by numerical simulations.

New ARQ or HARQ schemes taking into account the link between the MAC and IP layers have been recently introduced. In this paper, we analyze these new schemes in terms of delay and jitter by deriving these metrics in closed-form expressions at the IP level. As the framework developed for obtaining such terms in closed-form is generic, we show that the proposed expressions hold for any standard ARQ or HARQ scheme (ARQ, Incremental Redundancy HARQ, Chase Combining HARQ without cross-layer optimization) at any level (MAC or IP).