There are currently no mainstream
general-purpose processors built to operate on 128-bit integers or addresses,
though a number of processors do operate on 128-bit data.
The IBM System/370 could be considered the first
rudimentary 128-bit computer as it used 128-bit floating point registers.
Most modern CPUs feature SIMD instruction sets (SSE, AltiVec etc.) where 128-bit vector
registers are used to store several smaller numbers, such as four 32-bit floating-point
numbers, and a single instruction can operate on all these values in parallel.
However, these processors do not
operate on individual numbers that are 128 binary digits in length, only their registers have the size of 128-bits.
The DEC VAX supported operations on 128-bit
integer ('O' or octaword) and 128-bit floating-point ('H-float' or HFLOAT)
datatypes. Support for such operations was an upgrade option rather than being
a standard feature. Since the VAX's registers were 32-bits wide, a 128-bit
operation used four consecutive registers or four longwords in memory.
128-bit processors could become
prevalent as a method of addressing over 2^64 bits of information. Up to
2^128 could be directly addressed with 128 bits. That amount greatly
exceeds the total data stored on Earth today (2010), which has been
estimated to be around 1.2 zettabytes
(over 270 bytes).
Quadruple precision (128-bit) floating point numbers can store qword (64-bit) fixed point numbers or integers accurately without losing precision. Notice that since the 8087
(1980), x86 architecture supports 80-bit floating points that store and
process 64-bit signed integers (-263...263-1)
accurately.
The AS/400
virtual instruction set defines all pointers as 128-bit. This gets
translated to the hardware's real instruction set as required, allowing
the underlying hardware to change without needing to recompile the
software. Past hardware was 32-bit CISC, while current hardware is
64-bit PowerPC.
Because pointers are defined to be 128-bit, future hardware may be 128-bit
without software incompatibility.
Bluetooth
is a proprietaryopenwireless
technology standard for exchanging data over short distances (using
short-wavelength radio transmissions in the ISM band from
2400–2480 MHz) from fixed and mobile devices, creating personal area networks (PANs) with high
levels of security.
Created
by telecoms vendor Ericsson in 1994, it was originally conceived as a wireless
alternative to RS-232
data cables.
It
can connect several devices, overcoming problems of synchronization.
Bluetooth
is managed by the Bluetooth Special Interest Group,
which has more than 16,000 member companies in the areas of telecommunication,
computing, networking, and consumer electronics.
The
SIG oversees the development of the specification, manages the qualification
program, and protects the trademarks.
To
be marketed as a Bluetooth device, it must be qualified to standards
defined by the SIG.
Implementation
Bluetooth
uses a radio technology called frequency-hopping spread
spectrum, which chops up the data being sent and transmits chunks of it on
up to 79 bands- 1 MHz each.
1 MHz
each; centered from 2402 to 2480 MHz in the range 2,400–2,483.5 MHz allowing
for guard bands.
This
range is in the globally unlicensed Industrial, Scientific and Medical (ISM)
2.4 GHz short-range radio frequency band. It usually performs
800 hops per second, with AFH enabled.
One
master may communicate with up to 7 slaves in a piconet; all
devices share the master's clock.
Packet
exchange is based on the basic clock, defined by the master, which ticks at
312.5 µs intervals.
Two
clock ticks make up a slot of 625 µs; two slots
make up a slot pair of 1250 µs. In the simple case of single-slot packets
the master transmits in even slots and receives in odd slots; the slave,
conversely, receives in even slots and transmits in odd slots.
Packets
may be 1, 3 or 5 slots long but in all cases the master transmit will begin in
even slots and the slave transmit in odd slots.
Bluetooth
provides a secure way to connect and exchange information between devices such
as
A
master Bluetooth device can communicate with a maximum of seven devices in a piconet (an
ad-hoc computer network using Bluetooth technology), though not all devices
reach this maximum.
The
devices can switch roles, by agreement, and the slave can become the master
(for example, a headset initiating a connection to a phone will necessarily
begin as master, as initiator of the connection; but may subsequently prefer to
be slave).
The
Bluetooth Core Specification provides for the connection of two or more
piconets to form a scatternet, in which certain devices simultaneously play
the master role in one piconet and the slave role in another.
At
any given time, data can be transferred between the master and one other device
(except for the little-used broadcast mode.
The
master chooses which slave device to address; typically, it switches rapidly
from one device to another in a round-robin fashion.
Since
it is the master that chooses which slave to address, whereas a slave is (in
theory) supposed to listen in each receive slot, being a master is a lighter
burden than being a slave. Being a master of seven slaves is possible; being a
slave of more than one master is difficult. The specification is vague as to
required behaviour in scatternets.
Many
USB Bluetooth adapters or "dongles" are available,
some of which also include an IrDA adapter.
Older
(pre-2003) Bluetooth dongles, however, have limited capabilities, offering only
the Bluetooth Enumerator and a less-powerful Bluetooth Radio incarnation. Such
devices can link computers with Bluetooth with a distance of 100 meters, but
they do not offer as many services as modern adapters do.
Uses
Bluetooth is a standard wire-replacement
communications protocol primarily designed for low power consumption, with a
short range (power-class-dependent, but effective ranges vary in practice; see
table below) based on low-cost transceivermicrochips in each device.
Because the devices use a radio
(broadcast) communications system, they do not have to be in visual line of
sight of each other, however a quasi optical wireless path must be
viable.
The effective range varies due to propagation conditions, material coverage,
production sample variations, antenna configurations and battery conditions.
In most cases the effective range of
Class 2 devices is extended if they connect to a Class 1 transceiver,
compared to a pure Class 2 network. This is accomplished by the higher sensitivity
and transmission power of Class 1 devices.
While the Bluetooth Core Specification
does mandate minimums for range, the range of the technology is application
specific and is not limited. Manufacturers may tune their implementations to
the range needed for individual use cases.
Bluetooth
profiles
To use Bluetooth wireless technology, a
device has to be able to interpret certain Bluetooth profiles, which are
definitions of possible applications and specify general behaviors that
Bluetooth enabled devices use to communicate with other Bluetooth devices.
These profiles include settings to
parametrize and to control the communication from start. Adherence to profiles
saves the time for transmitting the parameters anew before the bi-directional
link becomes effective.
There are a wide range of Bluetooth
profiles that describe many different types of applications or use cases for
devices.
·Wireless
networking between PCs in a confined space and where little bandwidth is
required.
·Wireless
communication with PC input and output devices, the most common being the mouse,
keyboard and printer.
·Transfer
of files, contact details, calendar appointments, and reminders between devices
with OBEX.
·Replacement
of previous wired RS-232
serial communications in test equipment, GPS receivers, medical equipment, bar
code scanners, and traffic control devices.
·Allowing
a DECT phone to ring
and answer calls on behalf of a nearby mobile phone
·Real-time
location systems (RTLS), are used to track and identify the location of objects
in real-time using “Nodes” or “tags” attached to, or embedded in the objects
tracked, and “Readers” that receive and process the wireless signals from these
tags to determine their locations
·Personal
security application on mobile phones for prevention of theft or loss of items.
The protected item has a Bluetooth marker (e.g. a tag) that is in constant
communication with the phone. If the connection is broken (the marker is out of
range of the phone) then an alarm is raised. This can also be used as a man overboard
alarm. A product using this technology has been available since 2009.
Bluetooth
vs. Wi-Fi (IEEE 802.11)
Bluetooth and Wi-Fi (the brand name
for products using IEEE 802.11 standards) have some similar applications:
setting up networks, printing, or transferring files.
Wi-Fi is intended as a replacement for
cabling for general local area network access in work areas. This
category of applications is sometimes called wireless local area networks (WLAN).
Bluetooth was intended for portable
equipment and its applications. The category of applications is outlined as the
wireless personal area network (WPAN).
Wi-Fi is a wireless version of a common
wired Ethernet
network, and requires configuration to set up shared resources, transmit files,
and to set up audio links.
Wi-Fi uses the same radio frequencies as
Bluetooth, but with higher power, resulting in higher bit rates and better
range from the base station.
The nearest equivalents in Bluetooth are
the DUN profile, which allows devices to act as modem
interfaces, and the PAN profile, which allows for ad-hoc networking.
Devices
A Bluetooth USB dongle with a
100 m range. The MacBook Pro, shown, also has a built in Bluetooth
adaptor.
The technology is useful when
transferring information between two or more devices that are near each other
in low-bandwidth situations. Bluetooth is commonly used to transfer sound data
with telephones or byte data with hand-held computers (transferring files).
Bluetooth protocols simplify the
discovery and setup of services between devices. Bluetooth devices can
advertise all of the services they provide. This makes using services easier
because more of the security, network address and permission configuration can
be automated than with many other network types.
Computer requirements
A personal
computer that does not have embedded Bluetooth can be used with a Bluetooth
adapter that will enable the PC to communicate with other Bluetooth devices (such
as mobile
phones, mice and keyboards).
While some desktop
computers and most recent laptops come with a built-in Bluetooth radio, others will
require an external one in the form of a dongle.
Unlike its predecessor, IrDA, which requires a separate adapter
for each device, Bluetooth allows multiple devices to communicate with a
computer over a single adapter.
Specifications and features
The Bluetooth
specification was developed as a cable replacement in 1994 by Jaap
Haartsen and Sven Mattisson, who were working for Ericsson in Lund, Sweden.
The specifications
were formalized by the Bluetooth Special Interest Group
(SIG). The SIG was formally announced on May 20, 1998. Today it has a
membership of over 16,000 companies worldwide. It was established by Ericsson, IBM, Intel, Toshiba and Nokia, and later
joined by many other companies.
All versions of the Bluetooth standards
are designed for downward compatibility. That lets the latest standard cover
all older versions.
At this point you should know how to do computer controlled measurements.
However, the computer you use is probably connected to a network, and that
connection allows for some interesting possibilities. In particular, you
can take measurements and do control remotely. However, there are a few
topics you should be conversant with before you try that.
Why learn about Basic
Network Concepts?
Using computer measurement and control across a network allows for
possibilities of operation in remote or otherwise inaccessible locations, and
it allows for measurement and control of multiple locations from a single
location. To take advantage of those possibilities, you need to have a
basic familiarity with networked computers.
You need to learn about
basic concepts of network addressing and how to determine addresses. When
you are finished with this unit you should be able to use a program (LabVIEW)
to perform measurements and control across a network and you will learn about
URLs, and IP addresses, and how to determine them. In addition, you will
learn about some basic network concepts (servers, etc.)
Some Basic Network Concepts
Let's start with what happens when you "go to" www.SomeCompany.com to
get information about their products. Actually, you don't go anywhere,
but you do send some information across the network. The information you
send does the following.
First, the URL (www.SomeCompany.com) gets sent over the network to a special computer - a name server - that translates
this URL into an address of the form below. This form (all numbers)
is the numeric IP address.
www.xxx.yyy.zzz
Next, computers on the network (routers, etc.) try to send
the message along so that it will get to the right computer - i.e. the one
that has the IP address you are sending to. (Routers route messages
along the network, that's why they are called routers.
When the message gets to the correct computer - the server, wherever in the
world it might be - the server sends the file - often written in HTML -
back to your computer - the client.
This is an over-simplified picture of what goes on, but it contains all the
basic ideas about what happens. There are several points that you should
note in this sequence of events.
The message you - the client - send to the server has to
have the server's address, otherwise the message will not get to the
correct server.
The message you send to the server must also contain the
address of your computer, otherwise the information that the server sends
out on the network will not make it back to you.
The message you send to the server will also include a
command. The command to get an HTML file is GET. When you
are in a browser and you send a request for a file, you send a GET command
along with the name of the file you want to GET.
The message you send to the server may not go out as a
single message. It may be broken into packets, and each packet needs
to contain enough information that the complete information request can be
reassembled by the server.
The information sent back by the server may not arrive as a
single message. It will probably be broken into packets, and each
packet needs to contain enough information to permit your computer to
reassemble the complete file/set of information sent by the server.
In the above process when packets are sent over the
network, there are no guarantees that they will arrive in the correct
order, and computers on either end - both the client and the server - have
to have the capability of reassembling all of the information. In
the case of the client, you will often want that information displayed as
a web page.
That is a short summary of what takes place in a typical client-server
situation.
When you send a request for a web page to a URL (www.SomeCompany.com, for example) that information gets translated into an IP
address (www.xxx.yyy.zzz) by a Domain Name
Server (DNS). The DNS system has a vast
database that contains all of the URL-IP pairs. It changes constantly,
and it is probably the most highly accessed database on the planet.
