Update README

README.md

-# OpenXG-UDR
-
-
-
-OpenXG-UDR Arch
-```
-├── build:         Build directory, contains targets and object files generated by compilation of network functions. 
-    ├── scripts:   Directory containing scripts for building network functions.
-    ├── ext:       Directory containing spdlog and pistache and the JSON library.
-    └── UDR:       Directory containing object files generated by compilation of UDR network function. 
-├── etc:           Directory containing the configuration file to be deployed for UDR.
-└── src:           Source files of UDR.
-    ├── udr_app:   UDR Procedures handling logic. 
-    ├── common:    Common definitions for 3GPP specifications.
-    ├── model:     UDR service. 
-    ├── api:       UDR service.
-    └── impl:      UDR service.
-```
-    
-## Download source code from Gitlab
-```
-git clone http://git.opensource5g.org/openxg/openxg-udr.git
-cd openxg-udr/
-git checkout master
-```
-
-## install dependencies
-```
-cd ./build/scripts
-sudo ./build_udr -I
-```
-## build UDR
-```
-sudo ./build_udr -c -b Debug -j
-```
-## launch UDR
-```
-sudo ./build/UDR/udr -c etc/udr.conf -o
-```
\ No newline at end of file
+------------------------------------------------------------------------------
+
+                             OPENAIR-CN-5G
+ An implementation of the 5G Core network by the OpenAirInterface community.
+
+------------------------------------------------------------------------------
+
+OPENAIR-CN-5G is an implementation of the 3GPP specifications for the 5G Core Network.
+At the moment, it contains the following network elements:
+
+* Access and Mobility Management Function (**AMF**)
+* Authentication Server Management Function (**AUSF**)
+* Network Repository Function (**NRF**)
+* Session Management Function (**SMF**)
+* Unified Data Management (**UDM**)
+* Unified Data Repository (**UDR**)
+* User Plane Function (**UPF**)
+
+Each has its own repository: this repository (`oai-cn5g-udr`) is meant for UDR.
+
+# Licence info
+
+It is distributed under `OAI Public License V1.1`.
+See [OAI Website for more details](https://www.openairinterface.org/?page_id=698).
+
+The text for `OAI Public License V1.1` is also available under [LICENSE](LICENSE)
+file at the root of this repository.
+
+# Where to start
+
+The Openair-CN-5G UDR code is written, executed, and tested on UBUNTU server bionic version.
+Other Linux distributions support will be added later on.
+
+More details on the supported feature set is available on this [page](docs/FEATURE_SET.md).
+
+# Collaborative work
+
+This source code is managed through a GITLAB server, a collaborative development platform:
+
+*  URL: [https://gitlab.eurecom.fr/oai/cn5g/oai-cn5g-udr](https://gitlab.eurecom.fr/oai/cn5g/oai-cn5g-udr).
+
+Process is explained in [CONTRIBUTING](CONTRIBUTING.md) file.
+
+# Contribution requests
+
+In a general way, anybody who is willing can contribute on any part of the
+code in any network component.
+
+Contributions can be simple bugfixes, advices and remarks on the design,
+architecture, coding/implementation.
+
+# Release Notes
+
+They are available on the [CHANGELOG](CHANGELOG.md) file.
+
+# Repository Structure:
+
+The OpenAirInterface CN UDR software is composed of the following parts: 
+
+<pre>
+openair-cn5g-udr
+├── build:          Build directory, contains targets and object files generated by compilation of network functions. 
+    ├── log:        Directory containing build log files.
+    ├── scripts:    Directory containing scripts for building network functions.
+    └── udr:        Directory containing CMakefile.txt and object files generated by compilation of UDR network function. 
+├── ci-scripts:     Directory containing the script files for CI framework.
+├── docs:           Directory containing the documentation files.
+├── docker:         Directory containing the DockerFiles to build images.
+├── etc:            Directory containing the configuration file to be deployed for UDR.
+├── scripts:        Directory containing some scripts.
+└── src:            Source files of UDR.
+    ├── 5gaka:      Security algorimth implementation.
+    ├── api-server: UDR services APIs. 
+    ├── common:     Common header files
+    │   └── utils:  Common utilities.
+    ├── oai_udr:   UDR main directory, contains the "main" CMakeLists.txt file.
+    └── udr_app:   UDR network functions procedures and contexts.
+</pre>