Single Code Assignment Research Articles

Classification of user queries according to a hierarchical medical procedure encoding system using an ensemble classifier.

The Swiss classification of surgical interventions (CHOP) has to be used in daily practice by physicians to classify clinical procedures. Its purpose is to encode the delivered healthcare services for the sake of quality assurance and billing. For encoding a procedure, a code of a maximal of 6-digits has to be selected from the classification system, which is currently realized by a rule-based system composed of encoding experts and a manual search in the CHOP catalog. In this paper, we will investigate the possibility of automatic CHOP code generation based on a short query to enable automatic support of manual classification. The wide and deep hierarchy of CHOP and the differences between text used in queries and catalog descriptions are two apparent obstacles for training and deploying a learning-based algorithm. Because of these challenges, there is a need for an appropriate classification approach. We evaluate different strategies (multi-class non-terminal and per-node classifications) with different configurations so that a flexible modular solution with high accuracy and efficiency can be provided. The results clearly show that the per-node binary classification outperforms the non-terminal multi-class classification with an F1-micro measure between 92.6 and 94%. The hierarchical prediction based on per-node binary classifiers achieved a high exact match by the single code assignment on the 5-fold cross-validation. In conclusion, the hierarchical context from the CHOP encoding can be employed by both classifier training and representation learning. The hierarchical features have all shown improvement in the classification performances under different configurations, respectively: the stacked autoencoder and training examples aggregation using true path rules as well as the unified vocabulary space have largely increased the utility of hierarchical features. Additionally, the threshold adaption through Bayesian aggregation has largely increased the vertical reachability of the per node classification. All the trainable nodes can be triggered after the threshold adaption, while the F1 measures at code levels 3-6 have been increased from 6 to 89% after the threshold adaption.

Reduction in code blocking using scattered vacant codes for orthogonal variable spreading factor‐based wideband code division multiple access networks

3G and beyond wideband code division multiple access networks use orthogonal variable spreading factor (OVSF) codes to handle multimedia traffic. OVSF codes suffer from the limitation of code blocking, which leads to new call blocking. Scattered vacant codes in the OVSF code tree are the main cause of code blocking. This study proposes compact single code and multicode assignment schemes to reduce code blocking. The vacant codes used for incoming calls are the ones surrounded by a minimum number of consecutive vacant codes. Furthermore, finding consecutive vacant codes at the leaves of the tree is sufficient to find the consecutive vacant codes for all other layers. Handling non-quantised rates with a single code assignment produces wastage of code capacity, which is avoided with the use of a multicode assignment. Multicode usage facility along with the use of vacant codes from the minimum consecutive vacant code groups results in minimum code blocking. Two categories of the multicode assignment schemes are considered: the first one uses the least number of codes and is suitable for rake limited OVSF system, and the second scheme uses maximum number of codes to reduce code blocking significantly.

Code scattering and reduction in OVSF code blocking for 3G and beyond mobile communication systems

Scattered vacant codes in Orthogonal Variable Spreading Factor (OVSF) code based 3G and beyond WCDMA wireless networks leads to code blocking which further gives call blocking. The paper proposes four single code assignment schemes to reduce code scattering. The use of assignment scheme depends upon the type of input calls. The code reservation assignment (CRA) is used to efficiently handle one or higher rate class calls. It assigns priority number to the children of priority class codes such that the future availability of vacant codes in the priority layer is the highest. The remaining three code assignment schemes favors low to medium calls. The code assignment using group leaders uses busy codes (capacity) under predefined leaders to handle future calls. The code blocking in group leader approach can be reduced further if the used capacity of all the parents of the eligible vacant codes is examined and the code whose parent has maximum used capacity is used for new call. In adjacent vacant codes grouping scheme, the eligible vacant codes are listed to find code with least adjacent vacant codes. If unique result does not exists, the code (among the codes producing same adjacent vacant codes) with the least elapsed time of the busy neighbors is used for incoming call.

OVSF Code Assignment Schemes at the Forward Link of wcdm a Systems

In this paper we discuss code assignment schemes in wideband code division multiple access (WCDMA) systems based on orthogonal variable spreading factor (OVSF) codes. The OVSF codes are the limited resources in the forward link and their usage is critical for higher efficiency. The paper describes single code and multi code schemes for different requirements. In single code assignment category, adaptive code assignment (ADA) uses arrival distribution to reduce the number of code searches prior to finding a vacant candidate code. The time multiplexing in single code design makes code blocking zero with additional time slot management requirement. It provides additional benefit of handling non-quantized data rates. The next code precedence high (NCPH) scheme uses precedence numbers to make code assignment compact. The multi code scheme uses multiple codes to handle each call. Two multi code schemes are described, one aims to reduce complexity and the other aims to minimize code scattering and code blocking. The simulation results are demonstrated to show the number of code searches and call blocking variation for various code assignment schemes.

Partial Loss Probability of OVSF Single-code Assignment with Space-limited Batch Arrival Queues: M(2 X )/M/c/c

In a WCDMA Node-B, orthogonal variable spreading factor (OVSF) codes are both valuable and limited. Many efforts are being made to create OVSF code-assignment schemes that support a maximum number of users. Here the author (a) proposes a batch arrival and partial loss queuing model to evaluate OVSF single-code assignment system performance, and (b) derives expressions for calculating two important system performance measures (partial loss probability and bandwidth utilization) that respectively denote subscriber service quality and operator profit. Results from a simulation test suggest that the proposed model has utility in the construction of WCDMA networks.

Multiple Rake Combiners and Performance Improvement in 3G and Beyond WCDMA Systems

We propose an efficient code-assignment scheme utilizing multiple rake combiners to avoid the code-blocking problem in third-generation (3G) and beyond wideband code-division multiple-access (WCDMA) systems based upon orthogonal variable spreading factor (OVSF) channelization codes. The multiple rake combiners are required to be equipped with each base station (BS) and user equipment (UE). The major benefit of the proposed assignment scheme is in handling nonquantized data rates, making internal code fragmentation approximately zero. The task of code assignment to handle quantized data rates is divided into three steps. In the first step, the number of terms satisfying the capacity equation is found. The code combinations for all the terms in step 1 are found in step 2, which can be further subdivided into terms producing unique combinations and multiple combinations of terms. The procedure for finding the optimal code combination according to the number of rake combiners available at the UE and BS is given in step 3. Simulation results show the performance improvement in terms of reduction in blocking probability compared with existing single-code assignment schemes.

Markov Decision Process Based Multiple Codes Assignment in UMTS WCDMA Mobile Networks

For achieving high transmission rate in mobile multimedia communications, 3G WCDMA systems adopt the Orthogonal Variable Spreading Factor (OVSF) code tree to assign a single channelization code for each accepted connection. Based on the orthogonal characteristic of an OVSF code tree, an allocated code blocks the channelization codes that are on the descendant branches and the ancestral codes of the allocated code. Several researches have been proposed to overcome the code-blocking problem for maximizing system utilization. By using both the code assignment and reassignment mechanisms, the system utilization and code blocking can be improved. Nevertheless, the data rate of traffic classes in such single code assignment system should be powers of two of the basic rate, which is impractical and wastes the system capacity when the required rate is not powers of two of the basic rate. A good solution is to assign multiple codes to a new connection, but causes two drawbacks: high complexity of handling multiple codes and high cost from using more number of rake combiners. Consequently, there is a trade-off between waste rate and complexity of handling multiple codes assignments. In previous researches, high computation complexity of assigning multiple codes for a connection and large number of reassignment codes suppressed the advantage of reducing waste rate. Therefore, we propose an adaptive efficient partition algorithm with the Markov Decision Process (MDP) analysis approach to reduce the large number of reassignment codes while improving waste rate. There are two main motivations in the proposed approach. First, we propose an adaptive efficient partition algorithm to determine multiple codes based on the current state of the OVSF code tree for the new incoming connection. Second, after determining the multiple codes, we adopt the MDP analysis to assign the least-cost code for each determined code. Numerical results demonstrate that the proposed MDP approach yields the least number of reassignments and the least number of codes per connection while reducing waste rate significantly, as compared to other approaches.

Maximally flexible assignment of orthogonal variable spreading factor codes for multirate traffic

In universal terrestrial radio access (UTRA) systems, orthogonal variable spreading factor (OVSF) codes are used to support different transmission rates for different users. In this paper, we first define the flexibility index to measure the capability of an assignable code set in supporting multirate traffic classes. Based on this index, two single-code assignment schemes, nonrearrangeable and rearrangeable compact assignments, are proposed. Both schemes can offer maximal flexibility for the resulting code tree after each code assignment. We then present an analytical model and derive the call blocking probability, system throughput and fairness index. Analytical and simulation results show that the proposed schemes are efficient, stable and fair.