In this paper, we propose a new fair queueing algorithm to improve cell delay variation (CDV) for real-time service categories and to make efficient use of system resources for multimedia traffic in high speed ATM networks. The proposed algorithm is called the delay variation-based fair queueing (DVFQ) algorithm, which is based on per-VC queueing to improve CDV and fairness for each VC of real-time services such as CBR and rt-VBR. In DVFQ algorithm, we define two fairness indexes, which indicate the degree of the fairness of CDV at the rate of each VC, and the degree of impartially sharing the bandwidth between the scheduled cells for each VC. The simulation results for both heavily and lightly loaded conditions show that DVFQ algorithm provides better performances in terms of the CDV, the CDV fairness, and the service fairness than those of FCFS for real-time service.

This letter proposes a combined input- and crosspoint-queued (CIC) switch in which virtual output queuing (VOQ) is used at each input port. This CIC switch has a large buffer at each input port and a small buffer at each crosspoint. It does not require high-speed memory access or high-speed internal cell transmission lines. Since the performance of the CIC switch depends on the scheduling algorithms, we propose new scheduling algorithms for the CIC switch. Numerical results show that the mean cell delay time performance of the CIC switch using the proposed scheduling algorithms is better than that of an input-queued ATM switch. In addition, the required buffer size for the CIC switch using the proposed scheduling algorithms is smaller than that for a crosspoint-queued ATM switch.

This paper proposes the iterative quasi-oldest-cell-first (i-QOCF) scheduling algorithm, a new scheduling algorithm for input-queued ATM switches with virtual output queuing (VOQ). In the i-QOCF scheduling algorithm, each input port and each output port maintains its own list. The length of the list can be N, 2 N, ..., B N, where B is the size of the separate queue for an output port at input ports, and N is the number of output ports. The list maintained by an input port contains the identifiers for those output ports to which that input port will send a cell. The list maintained by an output port contains the identifiers for input ports that have a cell destined for that output port. If we use a list whose length is B N, then the identifiers in the list appear in the oldest order, and i-QOCF gives preference to cells that have been waiting for the longest time. If we use a list whose length is less than B N, then the identifiers in the list appear in the quasi-oldest order, and i-QOCF gives preference to cells that have been waiting for the quasi-longest time. We determine the performance of i-QOCF in a comparison with i-OCF in terms of cell delay time. We find that an input-queued ATM switch with i-QOCF and VOQ can achieve 100% throughput for independent arrival processes. Under uniform traffic, 3-QOCF is enough to achieve convergence during one cell time. If we use 3-QOCF, the list length is 3 N, then its cell delay time is almost the same as that of 4-OCF (Oldest-Cell-First).

Cell loss is one of the most important metrics of quality of service in ATM mobile communication systems. This loss can be suppressed by introducing buffer memories in the network, but that sacrifices delay. This paper proposes a lossless handover scheme for ATM mobile communication networks that can suppress delay fluctuations, and presents a subjective evaluation of MPEG2 images with various buffer memory sizes.

Cell delay variation (CDV) has been considered as an important performance measure due to the stringent timing requirement for video and multimedia services. In this paper we address the problem of CDV performance guarantee in virtual path (VP)-based ATM multiplexing. We propose a rate-based and non-work-conserving scheduling algorithm, called interleaved round robin (IRR), for serving traffic streams among VPs into the outgoing link. Through our performance analysis, the proposed scheme is capable of providing upper and lower bounds on the inter-visit time (IVT) for each VP, where the difference between the upper bound and the lower bound is simply dependent upon the number of multiplexed VPs. The distribution of VP IVT scheduled by an IRR server can also be well approximated using a random incidence technique. In addition to the VP-level CDV performance, we further examine the virtual connection (VC)-level CDV incurred within a multi-stage network through simulation study. The simulation results show that the IRR server can provide traffic regulation and smoothness at each network node. Moreover, the CDV distribution of a tagged VC is insensitive to the source traffic characteristic, node location, and the hop count traversed in the network.

A new simple cell spacing architecture that guarantees the peak cell interval and realizes preferential contention resolution is proposed. Scheduling the cell emission on departure of the previous cell, not arrival, allows the source peak cell interval to be regenerated without clumping. Priority control is also realized in the proposed spacer. A connection is scheduled either at the head or tail of the contention chain depending on its priority. The proposed method is applied to realize the UPC function. The proposed cell spacer eliminates the clumping effects of CDV completely and achieves high bandwidth efficiency.

The benefits of ATM techniques have been widely recognized and many organizations envisage the introduction of ATM techniques into their telecommunication networks. The ATM benefits can, however, be fully exploited only after effective network resource management techniques have been developed. This paper focuses on CBR-VP management techniques. The ATM transport network architecture and VP roles are summarized. Next, the issues of VP accommodation design are described. The point is how to create a design that accommodates cell loss and cell delay jitter, both of which depend on various network parameters and conditions. For this purpose, analytical procedures based on an M/D/1 queueing model are adopted. The approximation method is shown to be very effective in practical use through computer analysis. The method guarantees conservative QOSs. Finally, the proposed method is applied to several design examples to illustrate VP management issues. The proposed method will enable ATM techniques to be introduced to our telecommunication networks by the mid-1990's.

This letter proposes a new shaping algorithm (CRSA: CDV Reduction Shaping Algorithm) that can freely reduce the maximum CDV value of a cell stream to any predetermined value. There is a trade off between shaping delay and the maximum CDV value reduction achieved when using CRSA. The shaper using CRSA (CR-shaper) output satisfies the Peak Cell Rate Reference Algorithm set with the CR-shaper parameters.

For a CBR (Constant Bit Rate) connection in an ATM (Asynchronous Transfer Mode) network, we determine the CDV (Cell Delay Variation) tolerance for the mapping of ATM cells from the ATM Layer onto the Physical Layer. Our result will be useful to properly allocate resources to connections and to accurately enforce the contract governing the user's cell traffic by UPC (Usage Parameter Control).

In an ATM network, there are quality impairments particular to the ATM network such as cell loss and delay variation. During ATM network planning, therefore, various causes of quality impairments should be clarified. This paper overviews ATM network performance issues, and discusses performance requirements for the SDH network which will be applied as a physical layer of the ATM network. It also presents ATM network performance planning methods on cell loss and cell delay.