OVSF codes assignment and reassignment at the forward link of W-CDMA 3G systems

Rouskas, Angelos; Skoutas, Dimitrios N.

doi:10.1109/pimrc.2002.1046575

Cited by 52 publications

(42 citation statements)

References 7 publications

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“…The higher the ratio of chips per data symbol is, the higher data the rate will be. Observe that channelization codes in the WCDMA system normally adopt the orthogonal variable spreading factor (OVSF) codes [3][4][5]12,13,15,[17][18][19] to identify the down/up-link channels. Both down-links and up-links in a WCDMA system apply OVSF codes to match the requested data rate.…”

Section: Basic Idea and Challengesmentioning

confidence: 99%

“…The OVSF codes are arranged in a tree structure for code allocation purposes [3][4][5]12,13,15,[17][18][19]. The allocation rule of the OVSF code tree is shown in figure 3(a).…”

Section: Basic Idea and Challengesmentioning

confidence: 99%

“…Similarly, a long-length OVSF code, near the extremity of the OVSF code tree, offers a lower data rate. Some important properties of OVSF code trees are reviewed in [3][4][5]12,13,15,[17][18][19] and illustrated as follows.…”

Section: Basic Idea and Challengesmentioning

confidence: 99%

“…Many existing results are divided into OVSF-based and OVSF-like-based schemes, which are discussed as follows. OVSF-based schemes [3][4][5]12,13,15,[17][18][19] have been intensively investigated. Tseng et al [18,19] proposed single-OVSF code [18] and two-OVSF code [19] assignment/reassignment schemes in the WCDMA system.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A Fast Code-Assignment Strategy for a WCDMA Rotated-OVSF Tree with Code-Locality Capability

2005

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Abstract. In this paper, a new channelization code tree structure, namely an ROVSF (rotated-orthogonal variable spreading factor) code tree, is defined and investigated. Most existing code assignment schemes are investigated on the OVSF (orthogonal variable spreading factor) code tree in WCDMA systems. The main work of this investigation is to exploit and justify the new properties of the ROVSF code tree. We show that the ROVSF code tree offers the same code capability to that of the conventional OVSF code tree, but our ROVSF code tree additionally has the code-locality capability. With the code-locality capability, a fast code-assignment strategy is developed on the ROVSF code tree. Compared to existing code assignment schemes on OVSF code trees, a fast code assignment scheme is developed with lower search costs and a low blocking rate, due to its code-locality capability. Finally, the simulation results illustrate that our proposed scheme on the ROVSF code tree actually has lower search costs and a better blocking rate.

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Section: Basic Idea and Challengesmentioning

confidence: 99%

“…The OVSF codes are arranged in a tree structure for code allocation purposes [3][4][5]12,13,15,[17][18][19]. The allocation rule of the OVSF code tree is shown in figure 3(a).…”

Section: Basic Idea and Challengesmentioning

confidence: 99%

Section: Basic Idea and Challengesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Fast Code-Assignment Strategy for a WCDMA Rotated-OVSF Tree with Code-Locality Capability

2005

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“…1 gives a valid tree node assignment. The tree node assignment problem can be considered as a general resource allocation problem, which can model the specific problems, such as the Orthogonal Variable Spreading Factor (OVSF) code assignment problem [2,3,7,12,13,14,15,16,17], the buddy memory allocation problem [1,5,10,11], and the hypercube subcube allocation problem [6]. The main difference between these problems is how the resource, the nodes at level i, for 0 ≤ i ≤ h, are interpreted.…”

Section: Introductionmentioning

confidence: 99%

Online Tree Node Assignment with Resource Augmentation

Chan

Chin

Ting

et al. 2009

Lecture Notes in Computer Science

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Abstract. Given a complete binary tree of height h, the online tree node assignment problem is to serve a sequence of assignment/release requests, where an assignment request, with an integer parameter 0 ≤ i ≤ h, is served by assigning a (tree) node at level (or height) i and a release request is served by releasing a specified assigned node. The node assignments have to guarantee that no node is assigned to two assignment requests unreleased, and every leaf-to-root path of the tree contains at most one assigned node. With assigned node reassignments allowed, the target of the problem is to minimize the number of assignments/reassigments, i.e., the cost, to serve the whole sequence of requests. This online tree node assignment problem is fundamental to many applications, including OVSF code assignment in WCDMA networks, buddy memory allocation and hypercube subcube allocation.Most of the previous results focus on how to achieve good performance when the same amount of resource is given to both the online and the optimal offline algorithms, i.e., one tree. In this paper, we focus on resource augmentation, where the online algorithm is allowed to use more trees than the optimal offline algorithm. By using different approaches, we give (1) a 1-competitive online algorithm, which uses (h + 1)/2 trees, and is optimal because (h + 1)/2 trees are required by any online algorithm to match the cost of the optimal offline algorithm with one tree; (2) a 2-competitive algorithm with 3h/8 + 2 trees; (3) an amortized (4/3 + α)-competitive algorithm with (11/4 + 4/(3α)) trees, for any α where 0 < α ≤ 4/3.

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Delay Sensitivity Based Assignment of OVSF Codes for the Downlink DCH in WCDMA

Skoutas

Rouskas

2004

Lecture Notes in Computer Science

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Abstract. A significant problern that deteriorates the performance of 3G W-CDMA systems is code blocking. The complete elimination of this phenomenon is accomplished only if a code reassignment procedure is employed. However, the relatively high total signaling delay for a single OVSF code reassignment combined with the strict delay requirements of some services makes the reassignment of some OVSF codes impractical. In other words, that a reassignment procedure cannot always be performed and therefore code blocking cannot be eliminated. In this paper, we introduce a new code selection scheme, named Delay Sensitivity Based Assignment (DSBA) , which takes into account the different delay requirements of the incoming calls. The performance of the proposed scheme is evaluated through event driven simulation and the results show a significant decrease in code blocking probability, especially for high rate calls, compared to other previously proposed schemes.

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OVSF codes assignment and reassignment at the forward link of W-CDMA 3G systems

Cited by 52 publications

References 7 publications

A Fast Code-Assignment Strategy for a WCDMA Rotated-OVSF Tree with Code-Locality Capability

A Fast Code-Assignment Strategy for a WCDMA Rotated-OVSF Tree with Code-Locality Capability

Online Tree Node Assignment with Resource Augmentation

Delay Sensitivity Based Assignment of OVSF Codes for the Downlink DCH in WCDMA

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