Moby Dick Consolidated System Integration Plan

D0103v1.doc Version 1 6.7.2003
4.3.4.1 General architecture of the software platform
This section presents an overview of the basic hardware/software architecture. The platform is used to
implement the Time Division Duplex (TDD) transmission mode of the UMTS standard. The hardware
architecture is centred on a real-time PC system that gives access to, and allows experimenting with, wide
band radio resources. The platform is scalable and allows configurations from a powerful base station
with smart antennas to simpler mobile terminals with a single antenna. It provides functionality at three
levels: hardware, Digital Signal Processing (DSP) software, and link level software.
• Hardware Components
The hardware portion of the current testbed consists of 3 elements which are under software-control,
namely
• a PCI-bus based data acquisition card (PMC form-factor)
• an analogue/digital interface
• an up/down conversion RF card using TDD multiplexing
The radio portion is capable of generating arbitrary signals of a 5MHZ bandwidth in the 2110-2170 MHz
band using TDD multiplexing. A new radio interface is being produced for the 1900-1920 MHz band
(UMTS TDD).
• Software Components
The software portion of the platform is an extension to the Linux Operating System and makes use of a
hard real-time micro-kernel known as RT -Linux for performing layer 1 and layer 2 UMTS/TDD
processing. Networking functionality is provided by the Linux kernel and open-source extensions.
RT-Linux, an extension to the Linux Operating System, supports real-time interrupt handlers and realtime
periodic tasks with interrupt latencies and scheduling jitter close to hardware limits.
Real-time tasks in RT-Linux can communicate with Linux processes either via shared memory regions or
a FIFO interface. Thus, real-time applications can make use of all the powerful, non-real-time services of
Linux, including: Networking, Graphics, Windowing systems, Linux device drivers, Standard POSIX
functionality.
The configurations for Radio Gateways (RG), a combination of a base station and an IP router, and
Mobile Terminals (MT) are shown in figure 65 and figure 66.
IP Network (v4 v6)
Multi-CPU Linux Machine
/dev/srnet
/dev/eth0
Kernel
Space
Layer 1H/2/3
RT thread
Radio
Bearers
IP Networking subsystem
Linux Kernel
Server
Functions
PCI
Real-time
µKernel
DAQ
+
RF
Layer1L
RT thread
Real-time Space
User
Space
Figure 65: Radio Gateway Architecture
The RG’s network connection is IP based and is assumed to be connected to an IP network via Ethernet
using the standard Linux /dev/eth0 Ethernet device. The TD-CDMA to IP Network Interconnect is
made via a homemade RTLinux driver /dev/srnet. Its basic functions include
• Strict real-time implementation of 3GPP Layers 1 (PHY) and 2 (MAC/RLC)
• Adapted RRC signalling functionality to accommodate a set of mobile-IP management functions
(information broadcast, attachment, resource requests, paging, etc.)
The entities comprising the Radio Protocol Layers are collectively known as the Access Stratum (AS) in
3GPP terminology, whereas entities in the IP backbone are collectively known as the Non-Access
Stratum (NAS).
D0103v1.doc 87 / 168