Convolutional Codes Representation and Encoding

 Convolutional Codes
Representation and Encoding


§  Many known codes can be modified by an extra code symbol or by
    deleting a symbol
            * Can create codes of almost any desired rate
            * Can create codes with slightly improved performance
§ The resulting code can usually be decoded with only a slight
    modification to the decoder algorithm.
§ Sometimes modification process can be applied multiple times in
   succession

Modification to Known Codes


1.Puncturing:  delete a parity symbol
§(n,k) code ® (n-1,k) code
●
2.Shortening:    delete a message symbol
§(n,k) code ® (n-1,k-1) code
3.Expurgating:  delete some subset of codewords
§(n,k) code ® (n,k-1) code
4.Extending:  add an additional parity symbol
§(n,k) code ® (n+1,k) code
5.  Lengthening:  add an additional message symbol
§(n,k) code ® (n+1,k+1) code
6.  Augmenting:  add a subset of additional code words
§(n,k) code ® (n,k+1) code

Comments

Post a Comment

Popular posts from this blog

Handling of Skew

Handling of Skew 􀂄 The distribution of tuples to disks may be skewed — that is, some disks have many tuples, while others may have fewer tuples. 􀂄 Types of skew: 􀃌 Attribute-value skew. 􀂾 Some values appear in the partitioning attributes of many tuples; all the tuples with the same value for the partitioning attribute end up in the same partition. 􀂾 Can occur with range-partitioning and hash-partitioning. 􀃌 Partition skew. 􀂾 With range-partitioning, badly chosen partition vector may assign too many tuples to some partitions and too few to others. 􀂾 Less likely with hash-partitioning if a good hash-function is chosen. Handling Skew in Range-Partitioning 􀂄 To create a balanced partitioning vector (assuming partitioning attribute forms a key of the relation): 􀃌 Sort the relation on the partitioning attribute. 􀃌 Construct the partition vector by scanning the relation in sorted order as follows. 􀂾 After every 1/nth of the relation has been read, the value...
Read more

Fragment-and-Replicate Join

Fragment-and-Replicate Join 􀂄 Partitioning not possible for some join conditions 􀃌 e.g., non-equijoin conditions, such as r.A > s.B. 􀂄 For joins were partitioning is not applicable, parallelization can be accomplished by fragment and replicate technique 􀃌 Depicted on next slide 􀂄 Special case – asymmetric fragment-and-replicate: 􀃌 One of the relations, say r, is partitioned; any partitioning technique can be used. 􀃌 The other relation, s, is replicated across all the processors. 􀃌 Processor Pi then locally computes the join of ri with all of s using any join technique. 􀂄 General case: reduces the sizes of the relations at each processor. 􀃌 r is partitioned into n partitions,r0, r1, ..., r n-1;s is partitioned into m partitions, s0, s1, ..., sm-1. 􀃌 Any partitioning technique may be used. 􀃌 There must be at least m * n processors. 􀃌 Label the processors as 􀃌 P0,0, P0,1, ..., P0,m-1, P1,0, ..., Pn-1m-1. 􀃌 Pi,j computes the join of ri with sj. In ...
Read more

USER INTERFACE DESIGN FOR ANNA UNIVERSITY SYLLABUS

Unit – I Introduction Objective To Understand the definition and importance of User Interface Design To know about the concept, advantages and applications of GUI and Web interface User Interface Design Definition • User interface design is a subset of a field of study called human-computer interaction (HCI). Human-computer interaction is the study, planning, and design of how people and computers work together so that a person’s needs are satisfied in the most effective way. • The user interface is the part of a computer and its software that people can see, hear, touch, talk to, or otherwise understand or direct. The user interface has essentially two components: input and output. • Input is how people communicate his needs to the system using keyboard or any pointing device and output is how the system returns processing result to user through screen or sound. • The best interface is one which has proper design with combination of effective input and output mechanisms. Importance of...
Read more