Fruit juices - adding colour and health to your life

Easy to prepare, a good friend of your taste buds, a hit all through the year and good for your health – that’s a glass of fresh juice, which can also add glow and energy to your life. Fresh juice is healthy and we all know that drinking the real thing is better than the sugary alternatives that are packed months before they reach the consumers. Fresh juices benefit us in the following ways:

• They provide minerals, vitamins, essential fatty acids, carbohydrates and proteins
  
• Help improve energy levels
  
• Good for the skin
  
• Strengthen the immune system
  
• Make the bones stronger

Despite all the benefits that fruit juices offer, there are certain things we need to know about fresh juice.

Is it OK to drink as much juice as we want daily?

No, water should be the main source of liquid and it is always better to have fruits in their natural form rather than as juice. Why? Because we all add sugar and salt to the fruit juice we make at home. This increases the amount of sugar in our diet and thus, the calorie load. But we don’t really perceive drinks to be food. Eating a whole pomegranate or having three or four oranges in a row is a cumbersome job. But we would gallop a big glass of juice in a few seconds and even forget to count them as calories. So, if you take two servings of fruit in a juice, ideally you should forego your evening snacks.

Should we drink juice daily?

Drinking juice is an easy way to have two fruit servings per day that is good for the daily quota of vitamins. But, keep a check on the sugar added to the juice. It’s best to have fresh juice without any sugar or salt. Though such juice might taste a bit bland and sometimes sour as in the case of orange juice, you would gradually develop a taste for them. The best choice for a daily habit of juice is carrot, apple and ginger, made with only one piece of fruit. Carrots are sweet but lower in calories and have about half the carbohydrates of fruits. Celery is also a nice low-calorie filler. Have a look at the amount of carbohydrates different fruits have.

• Orange –16 g
  
• Grapes – 28 g
  
• Pomegranates – 26 g
  
• Pineapple – 19 g
  
• Apple – 21 g

How to use the juicer?

Now the next thing is how to use the juicer at home to get the best juice. The foremost thing is to get a good quality juicer, preferably ISI marked. If you want the fibre benefits, then put all the vegetables and fruits into a blender and don’t use a juice extractor. While ordering fresh juice from outside, be sure about the hygiene and ensure that they are using a blender, not an extractor. Extractors make a smooth drink but they remove the all-important fibre from the juice.

Are juices good for children?

Replacing water with juice for children can cause diarrhoea. Having juice everyday can help to develop lifetime sweet tendencies in children. So, juices should be an occasional drink for children. Eating fruit in its natural form and relying on water, as the source of liquid, are better alternatives. Nevertheless, fruit juice is better than having aerated drinks.

Tips on getting best out of your juices

• Always wash fruit and vegetables – even organic produce could carry bacteria.
  
• Include the stems and leaves of vegetables because they have a high vitamin and mineral content.
  
• Drink a juice within half an hour of preparing it, or it can get oxidised by exposure to air and develop a sour taste.
  
• If you must prepare juice early, keep it refrigerated with a tight lid. Or freeze in daily-serving- size containers immediately and drink it straight after thawing.
  
• Include the white inner skin of citrus fruits, as it is full of beneficial bioflavonoids.
  
• Add lemon juice to preserve the natural colour and reduce the oxidation of essential nutrients.
  
• If you want to lose weight, then drink vegetable juices, as they contain fewer calories than fruit juice.
  
• If you have a sensitive stomach or irritable bowel syndrome (IBS), ensure that you dilute juices with water (three parts of juice with one part of water).

Easy to make juice-based drinks

Watermelon drink

Ingredients - 3 cups watermelon (washed and cut into small pieces), sugar (as per taste), 3 tablespoon skimmed milk, ice cubes.

Method - Blend the ingredients in a blender and refrigerate. Pour the prepared drink into serving glass, add ice cubes and serve.

Nutritive value of the watermelon juice - Apart from providing energy, watermelon protects against age-related symptoms of vision loss, fights heart disease, reduces cancer risk and is loaded with anti-oxidants. So, a glass of watermelon drink everyday not only quenches your thirst but also offers a range of health benefits.

Carrot, celery and cabbage juice

Ingredients - 2 cucumbers, stalks of celery, a piece of ginger, a handful of parsley, piece of apple or citrus fruit

Method - Wash all vegetables and juice them together. Serve it fresh.

A glass of fruit or vegetable juice takes very little digestion. It goes right into your body and is a very yummy way of getting instant energy. Fruit juices can energise your life.

IEEE 802.11n

IEEE 802.11n is a proposed amendment to the IEEE 802.11-2007 wireless networking standard to significantly improve network throughput over previous standards, such as 802.11b and 802.11g, with a significant increase in the maximum raw (PHY) data rate from 54 Mbit/s to a maximum of 600 Mbit/s. The current state of the art supports a PHY rate of 300 Mbit/s, with the use of 2 spatial streams at a channel width of 40 MHz. Depending on the environment, this may translate into a user throughput (TCP/IP) of 100 Mbit/s.

IEEE 802.11n builds on previous 802.11 standards by adding multiple-input multiple-output (MIMO) and Channel-bonding/40 MHz operation to the physical (PHY) layer, and frame aggregation to the MAC layer.

MIMO uses multiple transmitter and receiver antennas to improve the system performance. MIMO is a technology which uses multiple antennas to coherently resolve more information than possible using a single antenna. Two important benefits it provides to 802.11n are antenna diversity and spatial multiplexing.

MIMO technology relies on multipath signals. Multipath signals are the reflected signals arriving at the receiver some time after the line of sight (LOS) signal transmission has been received. In a non-MIMO based 802.11a/b/g network, multipath signals were perceived as interference degrading a receiver's ability to recover the message information in the signal. MIMO uses the multipath signal's diversity to increase a receiver's ability to recover the message information from the signal.

Another ability MIMO technology provides is Spatial Division Multiplexing (SDM). SDM spatially multiplexes multiple independent data streams, transferred simultaneously within one spectral channel of bandwidth. MIMO SDM can significantly increase data throughput as the number of resolved spatial data streams is increased. Each spatial stream requires a discrete antenna at both the transmitter and the receiver. In addition, MIMO technology requires a separate radio frequency chain and analog-to-digital converter for each MIMO antenna which translates to higher implementation costs compared to non-MIMO systems.

Channel Bonding, also known as 40 MHz, is a second technology incorporated into 802.11n which can simultaneously use two separate non-overlapping channels to transmit data. Channel bonding increases the amount of data that can be transmitted. 40 MHz mode of operation uses 2 adjacent 20 MHz bands. This allows direct doubling of the PHY data rate from a single 20 MHz channel. (Note however that the MAC and user level throughput will not double. Coupling MIMO architecture with wider bandwidth channels offers the opportunity of creating very powerful yet cost-effective approaches for increasing the physical transfer rate.

Data encoding

The transmitter and receiver use precoding and postcoding techniques, respectively, to achieve the capacity of a MIMO link. Precoding includes spatial beamforming and spatial coding, where spatial beamforming improves the received signal quality at the decoding stage. Spatial coding can increase data throughput via spatial multiplexing and increase range by exploiting the spatial diversity, through techniques such as Alamouti coding.

Number of antennas

The number of simultaneous data streams is limited by the minimum number of antennas in use on both sides of the link. However, the individual radios often further limit the number of spatial streams that may carry unique data. The a X b : c notation helps identify what a given radio is capable of. The first number (a) is the maximum number of transmit antennas or RF chains that can be used by the radio. The second number (b) is the maximum number of receive antennas or RF chains that can be used by the radio. The third number (c) is the maximum number of data spatial streams the radio can use. For example, a radio that can transmit on two antennas and receive on three, but can only send or receive two data streams would be 2 X 3 : 2.

The 802.11n draft allows up to 4 X 4 : 4. Common configurations of 11n devices are 2 X 2 : 2, 2 X 3 : 2, and 3 X 3 : 2. All three configurations have the same maximum throughputs and features, and differ only in the amount of diversity the antenna systems provide.

Frame aggregation

PHY level data rate improvements do not increase user level throughput beyond a point because of 802.11 protocol overheads, like the contention process, interframe spacing, PHY level headers (Preamble + PLCP) and acknowledgment frames. The main medium access control (MAC) feature that provides a performance improvement is aggregation. Two types of aggregation are defined:

1. Aggregation of MAC Service Data Units (MSDUs) at the top of the MAC (referred to as MSDU aggregation or A-MSDU)
2. Aggregation of MAC Protocol Data Units (MPDUs) at the bottom of the MAC (referred to as MPDU aggregation or A-MPDU)

Aggregation is a process of packing multiple MSDUs or MPDUs together to reduce the overheads and average them over multiple frames, thus increasing the user level data rate. A-MPDU aggregation requires the use of Block Acknowledgement or BlockAck, which was introduced in 802.11e and has been optimized in 802.11n.

Backward compatibility

When 802.11g was released to share the band with existing 802.11b devices, it provided ways of ensuring coexistence between the legacy and the new devices. 802.11n extends the coexistence management to protect its transmissions from legacy devices, which include 802.11g, 802.11b and 802.11a. There are MAC and PHY level protection mechanisms as listed below:

1. PHY level protection: Mixed Mode Format protection (also known as L-SIG TXOP Protection): In mixed mode, each 802.11n transmission is always embedded in an 802.11a or 802.11g transmission. For 20 MHz transmissions, this embedding takes care of the protection with 802.11a and 802.11g. However, 802.11b devices still need CTS protection.
2. PHY level protection: Transmissions using a 40 MHz channel in the presence of 802.11a or 802.11g clients require using CTS protection on both 20 MHz halves of the 40 MHz channel, to prevent interference with legacy devices.
3. PHY level protection: An RTS/CTS frame exchange or CTS frame transmission at legacy rates can be used to protect subsequent 11n transmission.

Even with protection, large discrepancies can exist between the throughput an 802.11n device can achieve in a greenfield network, compared to a mixed-mode network, when legacy devices are present. This is an extension of the 802.11b/802.11g coexistence problem.

Deployment Strategies

To achieve maximum throughput a pure 802.11n 5 GHz network is recommended. The 5 GHz band has substantial capacity due to many non-overlapping radio channels and less radio interference as compared to the 2.4 GHz band.[3] An 802.11n-only network may be impractical for many users because the existing computer stock is predominantly 802.11b/g only. Replacement of incompatible WiFi cards or of entire laptop stock is necessary for older computers to operate on the network. Consequently, it may be more practical in the short term to operate a mixed 802.11b/g/n network until 802.11n hardware becomes more prevalent. In a mixed-mode system, it’s generally best to use a dual-radio access point and place the 802.11b/g traffic on the 2.4 GHz radio and the 802.11n traffic on the 5 GHz radio.[4]

Wi-Fi Alliance

As of mid-2007, the Wi-Fi Alliance has started certifying products based on IEEE 802.11n Draft 2.0.[6] This certification program established a set of features and a level of interoperability across vendors supporting those features, thus providing one definition of 'draft n'. The Baseline certification covers both 20 MHz and 40 MHz wide channels, and up to two spatial streams, for maximum throughputs of 144.4 Mbit/s for 20 MHz and 300 Mbit/s for 40 MHz (with Short Guard interval). A number of vendors in both the consumer and enterprise spaces have built products that have achieved this certification.[7] The Wi-Fi Alliance certification program subsumed the previous industry consortium efforts to define 802.11n, such as the now dormant Enhanced Wireless Consortium (EWC). The Wi-Fi Alliance is investigating further work on certification of additional features of 802.11n not covered by the Baseline certification, including higher numbers of spatial streams (3 or 4), Greenfield Format, PSMP, Implicit & Explicit Beamforming and Space-Time Block Coding.